194A - Exams - CodeForces Solution

#include <bits/stdc++.h>
 
using namespace std;
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int exams, mark, ans=0;
    cin>>exams>>mark;
    ans = exams * 2;
    ans = mark - ans; 
    if(ans < exams) cout<<exams - ans;
    else cout<< 0; 
    return 0;
}