#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001



int main(){
	
	double A,B,C;
	cin>>A>>B>>C;
	
	double ans = A+B;
	ans *= 1.0 + C;
	
	long long a = round(ans);
	cout<<a<<endl;
	
	return 0;
}