#include <stdio.h>
int ain(){
    int weight,speed;
    float balance,tilt;
    scanf("%d",&weight);
    scanf("%d",&speed);
    scanf("%f",&balance);
    scanf("%f",&tilt);
    if(weight<=0|| speed<=0||balance<=0||tilt<=0){
        printf("invalid input");

    }else{
        float stability=(weight* speed)/(balance+tilt);
        printf("%0.2f",stability);
        
    }
    return 0;
}