Kyselyt

#include <iostream>
using namespace std;

int main() {
    int q;
    cin >> q;
    for(int i=0; i!=q; ++i) {
        unsigned long long k;
        cin >> k;

        unsigned long long l = 1; // smallest number in partial series
        unsigned long long n = 9; // numbers in partial series
        unsigned long long dc = 9; // digits in this and past partial series
        unsigned long long dn = 1; // digit per number in partial series
        while (k > dc) {
            l*=10;
            n*=10;
            dn+=1;
            dc+=dn*n;
        }
        unsigned long long kps = k-dc+dn*n; // k in partial series
        unsigned long long number = l+(kps-1)/dn; // number matching k
        unsigned long long digitIndex = dn - 1 - ( (kps-1)%dn ); // index of matched digit
        unsigned long long digitModulo = 10;
        for (unsigned long long i=0; i!=digitIndex; ++i) {
            digitModulo*=10;
        }
        unsigned long long digitDivider = digitModulo/10;
        if (digitDivider==0) digitDivider=1;
        unsigned long long digit = (number%digitModulo)/digitDivider;

        cout << digit << endl;
    }
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: ACCEPTED