#include<bits/stdc++.h>
#define ll long long
using namespace std;
int main(){
	ll a,b,c;
	cin>>a>>b>>c;
	ll s;
	s=ceil((3.5*(a+b+c)-a*2-b*3-c*4)/1.5);
	if(s<=0){
		cout<<0;
		return 0;
	}
	cout<<s;
	return 0;
}