#include <iostream>
#include <cmath>
using namespace std;
 
int main(){
    float k, n, m, d, s;
    cin >> k >> n >> m >> d;
    s = (d * k * n * m) / (k * n * m - k * m - k * n - m * n);
    if((1/k + 1/n + 1/m >= 1) || (floor(s/k) != s/k || floor(s/n) != s/n || floor(s/m) != s/m) || !(floor(s) == s)){
	cout << "-1";
    }else{
    	cout << s;
    }
    
    return 0;
}