#include<bits/stdc++.h>
using namespace std;
int main(){
    long long N,M,p,q;
    scanf("%lld%lld%lld%lld",&N,&M,&p,&q);
    if((p-1)*N+q<=N*M) printf("Program ends with return value 0.");
    else printf("Segmentation fault.");
    return 0;
}