// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <climits>
#include <cmath>
#include <complex>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <tuple>
#include <vector>
using namespace std;
using lg = long long;
using pii = pair<int, int>;
using pll = pair<lg, lg>;
#define TEST cerr << "TEST" << endl
#define AMARI 998244353
// #define AMARI 1000000007
#define TEMOTO ((sizeof(long double) == 16) ? false : true)
#define TIME_LIMIT 1980 * (TEMOTO ? 1 : 1000)
#define mpr make_pair
#define el '\n'
#define El '\n'

#define MULTI_TEST_CASE false 
void solve(void) {
    int w,z;
    double b;
    cin >> w >> z >> b;
    int ans = (w + z) * (b + 1);
    cout << ans << el;
    return;
}

void calc(void) {
    return;
}

int main(void) {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    calc();
    int t = 1;
    if(MULTI_TEST_CASE) cin >> t;
    while(t--) {
        solve();
    }
    return 0;
}