#include using namespace std; int main() { int a,b,c,n; cin>>n>>a>>b>>c; cout<<n-(a-c)-(b-c)-c; return 0; }

#include<bits/stdc++.h>


using namespace std; 
int main() {
    float num;
   cin>>num;
    printf("%.3f", num); 
    return 0;
}