kusac

#include <bits/stdc++.h>
#define ll long long
#define INF 999999999
#define N (1<<17)
#define M 1000000007

using namespace std;

int main () {
  int n, m;
  cin>>n>>m;
  n = n % m;
  int ans = 0;
  if (!n) cout<<0<<endl;
  else if (n == m) cout<<0<<endl;
  else if (n < m) {
    int l = m;
    ans += n * (l / n);
    l %= n;
    if (!l) ans -= n;
    if (l) {
      if (n % l) {
	ans += l - 1;
      }
      else if (m % l) {
	ans += l - 1;
      }
    }
    cout<<ans<<endl;
  }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: ACCEPTED