DIENTICH C++

#include <bits/stdc++.h>
using namespace std;

float sv,st;
int main()
{
    freopen("dientich.inp","r",stdin);
    freopen("dientich.out","w",stdout);
    cin>>sv;
    //scanf("%f",&sv);
    st=(sv/4)*3.14;
    //printf("dien tich hinh tron la %0.6f",s2);
    cout<<"Dien tich hinh tron la "<<setprecision(6)<<fixed<<st;
}