#include <bits/stdc++.h>
using namespace std;
int main(){
    int m=17,n=25;
    for(int i=1;;i++){
        m--;
        n++;
        if(n/m==2){
            cout<<i;
            break;
        }
    }
}
/**************************************************************
	Problem: 1349
	User: wngjinming
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/