#include<iostream>
#include<iomanip>
using namespace std;
int main(){
    double marks[4];
    float sum;
    for(int i -0 ; i<4; i++);{
        cout<<"Invalid input";
        return 0;
    }
    else{
        sum+marks[i];
    }
    sum = sum/4;
    cout<<fixed<<setprecision(2)<<sum;
    
    return 0;
}