#include <bits/stdc++.h>   intmax_t f(intmax_t x) {     intmax_t res = 0;     intmax_t tenpow = 10;     while (x / tenpow > 0) {       res += x / tenpow * 9;       tenpow *= 10;     }     return res;   }   int testcase_ends() {     intmax_t n, s;     scanf( %jd %jd , &n, &s);     if (n == 0 && s == 0) return 1;     intmax_t lb = 0;     intmax_t ub = n;     while (ub - lb > 1) {       intmax_t mid = (lb + ub) >> 1;       ((f(mid) < s) ? lb : ub) = mid;     }     intmax_t res = n - lb;     if (f(ub) < s) res = 0;     printf( %jd n , res);     return 0;   }   int main() { testcase_ends(); }   