/**
 *    author:  tđq
**/
#include <bits/stdc++.h>
#define task ""

using namespace std;

typedef long long ll;

const ll nmax = 1e5 + 5;

double a, b, c;
int main()
{

 //freopen(task".inp" , "r" , stdin);
 //freopen(task".out" , "w" , stdout);

 ios::sync_with_stdio(false);
 cin.tie(0);

 cin >> a >> b >> c; 
 cout << setprecision(2) << fixed << (double) a * a - b * b + c * c * c;
 return 0; 
}