#include <iostream>
int main(){
    int Px,Py,Qx,Qy;
    std::cin >> Px >> Py >> Qx >> Qy;
    if(Px < 0)Px = Px + (Px * -2);
    if(Py < 0)Py = Py + (Py * -2);
    if(Qx < 0)Qx = Qx + (Qx * -2);
    if(Qy < 0)Qy = Qy + (Qy * -2);
    int PL = Px - Py; if(PL < 0)PL = PL + (PL * -2);
    int QL = Qx - Qy; if(QL < 0)QL = QL + (QL * -2);
    double SL = (double)PL / (double)QL;
    std::cout << SL << std::endl;
    return 0;
}