#include <iostream>

using namespace std;
typedef long long ll;

int main() {
  ll A, B;
  cin >> A >> B;

  ll ans;

  if(A < 0){
    ans = A % B;
    if(ans < 0)
      ans += abs(B);
  }
  else{
    ans = A % B;
  }

  cout << ans << endl;
  return 0;
}