#include <bits/stdc++.h>   using namespace std;   int A, B, C, N;   int main() {     scanf( %d%d%d%d , &A, &B, &C, &N);     if (A < C || B < C || A + B >= N + C)       puts( -1 );     else       printf( %d n , N - (A + B - C));   }   