poj 2521 How much did the bus...

#include <iostream>#include <cstdlib>#include <cstring>#include <cstdio>using namespace std;int main(){      int m, p, n, c;    while (scanf("%d%d%d%d", &n, &m, &p, &c) != EOF && !(n == 0 && m == 0 && p == 0 && c == 0))        printf("%dn", -(m - n - p));    return 0;}