### The Problem

Work out the first 10 digits of the sum of a lot of really large numbers.

I won’t duplicate the list of numbers here since they exist in code form in the solution

### The Solution

The problem requires us to sum 100 50-digit integers.

This might cause problems in other languages, but thanks to the .NET Framework’s big integer type, the problem is almost trivially easy. We simply parse the input into `bigint` and then take the sum. We could even skip the parsing step by specifying the numbers as `bigint` literals (e.g. `1234I`), but where’s the sport in that?

``````open System.Numerics

let input = [
"37107287533902102798797998220837590246510135740250"
"46376937677490009712648124896970078050417018260538"
"74324986199524741059474233309513058123726617309629"
"91942213363574161572522430563301811072406154908250"
"23067588207539346171171980310421047513778063246676"
"89261670696623633820136378418383684178734361726757"
"28112879812849979408065481931592621691275889832738"
"44274228917432520321923589422876796487670272189318"
"47451445736001306439091167216856844588711603153276"
"70386486105843025439939619828917593665686757934951"
"62176457141856560629502157223196586755079324193331"
"64906352462741904929101432445813822663347944758178"
"92575867718337217661963751590579239728245598838407"
"58203565325359399008402633568948830189458628227828"
"80181199384826282014278194139940567587151170094390"
"35398664372827112653829987240784473053190104293586"
"86515506006295864861532075273371959191420517255829"
"71693888707715466499115593487603532921714970056938"
"54370070576826684624621495650076471787294438377604"
"53282654108756828443191190634694037855217779295145"
"36123272525000296071075082563815656710885258350721"
"45876576172410976447339110607218265236877223636045"
"17423706905851860660448207621209813287860733969412"
"81142660418086830619328460811191061556940512689692"
"51934325451728388641918047049293215058642563049483"
"62467221648435076201727918039944693004732956340691"
"15732444386908125794514089057706229429197107928209"
"55037687525678773091862540744969844508330393682126"
"18336384825330154686196124348767681297534375946515"
"80386287592878490201521685554828717201219257766954"
"78182833757993103614740356856449095527097864797581"
"16726320100436897842553539920931837441497806860984"
"48403098129077791799088218795327364475675590848030"
"87086987551392711854517078544161852424320693150332"
"59959406895756536782107074926966537676326235447210"
"69793950679652694742597709739166693763042633987085"
"41052684708299085211399427365734116182760315001271"
"65378607361501080857009149939512557028198746004375"
"35829035317434717326932123578154982629742552737307"
"94953759765105305946966067683156574377167401875275"
"88902802571733229619176668713819931811048770190271"
"25267680276078003013678680992525463401061632866526"
"36270218540497705585629946580636237993140746255962"
"24074486908231174977792365466257246923322810917141"
"91430288197103288597806669760892938638285025333403"
"34413065578016127815921815005561868836468420090470"
"23053081172816430487623791969842487255036638784583"
"11487696932154902810424020138335124462181441773470"
"63783299490636259666498587618221225225512486764533"
"67720186971698544312419572409913959008952310058822"
"95548255300263520781532296796249481641953868218774"
"76085327132285723110424803456124867697064507995236"
"37774242535411291684276865538926205024910326572967"
"23701913275725675285653248258265463092207058596522"
"29798860272258331913126375147341994889534765745501"
"18495701454879288984856827726077713721403798879715"
"38298203783031473527721580348144513491373226651381"
"34829543829199918180278916522431027392251122869539"
"40957953066405232632538044100059654939159879593635"
"29746152185502371307642255121183693803580388584903"
"41698116222072977186158236678424689157993532961922"
"62467957194401269043877107275048102390895523597457"
"23189706772547915061505504953922979530901129967519"
"86188088225875314529584099251203829009407770775672"
"11306739708304724483816533873502340845647058077308"
"82959174767140363198008187129011875491310547126581"
"97623331044818386269515456334926366572897563400500"
"42846280183517070527831839425882145521227251250327"
"55121603546981200581762165212827652751691296897789"
"32238195734329339946437501907836945765883352399886"
"75506164965184775180738168837861091527357929701337"
"62177842752192623401942399639168044983993173312731"
"32924185707147349566916674687634660915035914677504"
"99518671430235219628894890102423325116913619626622"
"73267460800591547471830798392868535206946944540724"
"76841822524674417161514036427982273348055556214818"
"97142617910342598647204516893989422179826088076852"
"87783646182799346313767754307809363333018982642090"
"10848802521674670883215120185883543223812876952786"
"71329612474782464538636993009049310363619763878039"
"62184073572399794223406235393808339651327408011116"
"66627891981488087797941876876144230030984490851411"
"60661826293682836764744779239180335110989069790714"
"85786944089552990653640447425576083659976645795096"
"66024396409905389607120198219976047599490197230297"
"64913982680032973156037120041377903785566085089252"
"16730939319872750275468906903707539413042652315011"
"94809377245048795150954100921645863754710598436791"
"78639167021187492431995700641917969777599028300699"
"15368713711936614952811305876380278410754449733078"
"40789923115535562561142322423255033685442488917353"
"44889911501440648020369068063960672322193204149535"
"41503128880339536053299340368006977710650566631954"
"81234880673210146739058568557934581403627822703280"
"82616570773948327592232845941706525094512325230608"
"22918802058777319719839450180888072429661980811197"
"77158542502016545090413245809786882778948721859617"
"72107838435069186155435662884062257473692284509516"
"20849603980134001723930671666823555245252804609722"
"53503534226472524250874054075591789781264330331690"
]

let sum =
input
|> Seq.map BigInteger.Parse
|> Seq.sum

sum.ToString().Substring(0, 10)

``````
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