#include<iostream>
using namespace std;

int main(){
    try{
        float num,d;float g;
        cin>>num>>d;
        if(d==0){
            throw "-1";
        }
        
        g = num/d;
        cout<<fixed<<setprecision(2)<<g;
    }
    catch(const char* msg){
        cout<<msg;
    }
    return 0;
    
}