#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm> 
#include<string>
#include<cstring>
using namespace std;
int main()
{
    double a, b, c;
    cin >> a >> b >> c;
    double sum1 = 0,sum2 = 0 ,sum3 = 0;
    for (int i = 1; i <= a; i++) {
        sum1 += i;
    }
    for (int i = 1; i <= b; i++) {
        sum2 += i * i;
    }
    for (int i = 1; i <= c; i++) {
        sum3 += 1.0 / i;
    }
    double sum = sum1 + sum2 + sum3;
    printf("%.2lf", sum);

    return 0;
}