#include <bits/stdc++.h>
using namespace std;

#ifdef DEBUG_
#include <compe/debug.hpp>
#else
#define dump(...)
#endif

#define FastIO cin.tie(nullptr), ios_base::sync_with_stdio(false);
#define rep(i, n) for (int i = 0; (int)i < n; ++i)
#define repa(i, a, n) for (int i = a; (int)(i) < (n); (++i))
#define rrep(i, n) for (int i = (n - 1); (int)i >= 0; --i)
#define rrepa(i, a, n) for (int i = a; (int)i >= 0; --i)
#define EACH(x, a) for (auto& x : a)
#define output(msg) cout << msg << '\n'
#define die(msg)         \
  do {                   \
    cout << msg << endl; \
    exit(0);             \
  } while (0)

template <typename T> bool chmax(T& a, const T& b) {
  return ((a < b) ? (a = b, true) : (false));
}
template <typename T> bool chmin(T& a, const T& b) {
  return ((a > b) ? (a = b, true) : false);
}

using llint = long long int;

int main() {
  FastIO;
  double w, z;
  double b;
  cin >> w >> z >> b;

  double bonus{w + z};
  bonus += w * b;
  bonus += z * b;
  output((int)bonus);
}