#include <stdio.h>

int main () {
  long long n = 0LL;
  int e = 0;
  
  int res = 0;
  
  long long ans = -1LL;
  long long d = 1LL;
  
  res = scanf("%lld", &n);
  res = scanf("%d", &e);
  
  while (e > 0) {
    d *= 5LL;
    e--;
  }
  
  if (n > 0LL) {
    n %= d;
  } else {
    n = (d-(-n)%d)%d;
  }
  
  if (d < 100000LL) {
    for (long long i = 0LL; i < d; i += 1LL) {
      if (ans < 0LL && (i*i)%d == n) {
        ans = i;
      }
    }
  } else {
    while (ans < 0LL && n <= (1LL<<29LL)) {
      long long idx[2] = { 0LL, n+1LL };
      while (idx[1]-idx[0] > 1LL) {
        long long nxt = (idx[0]+idx[1])/2LL;
        if (nxt*nxt <= n) {
          idx[0] = nxt;
        } else {
          idx[1] = nxt;
        }
      }
      if (idx[0]*idx[0] == n) {
        ans = idx[0];
      } else {
        n += d;
      }
    }
  }
  
  if (ans < 0LL) {
    printf("NaN\n");
  } else {
    printf("%lld\n", ans);
  }
  
  return 0;
}