View Code of Problem 2217

#include<stdio.h>
#include<algorithm>
#include<iostream>
#include<string.h>
using namespace std;

int main(void){
	int a,b,c,d;
	while(cin>>a>>b>>c>>d){
		if(a==0&&b==0&&c==0&&d==0)
			break;
		cout<<a-b+c<<endl;
	}
}