#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: wangyiyang
	Language: C++
	Result: Accepted
	Time:4 ms
	Memory:2072 kb
****************************************************************/