#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>
#include <limits>
#include <array>

static const int MOD = 998244353;
using ll = long long;
using uint = unsigned;
using ull = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;


int main() {
    int w, z;
    cin >> w >> z;
    double b;
    cin >> b;
    double ans = (w+z)*(1+b);
    cout << int(ans) << "\n";
    return 0;
}