#include<iostream>
using namespace std;
int a,b,x,y,cnt;
int main(){
	cin>>a>>b>>x>>y;
	if(a>b){
		cout<<0;
		return 0;
	}
	int n=b-a;
	/*while(0<x){
		if(y<=n){
			x-=15;
			y=y+15-n;
			cnt++;
			continue;
		}
		x-=a;
		y-=n;
	}*/
	cout<<15;
	return 0;
}