............

#include <bits/stdc++.h>
using namespace std;
int main()
{
    long double a,b,c,s1,s2,s3;
    long double pi=3.1415926535;
    double n;
    cin>>a>>b>>c;
    s1=a*c;
    s2=(pi*c*c)/4;
    s3=b*(a+c);
    n=s1+s2+s3;
    n=n/10000;
    printf("%.3f\n",n);
    return 0;
}