#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;

void IO(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
}

int main(){
  IO();
  ld w,z,b;
  cin>>w>>z>>b;
  cout<<((w+z)*(b+1.0))<<endl;
}