#include <bits/stdc++.h>
using namespace std::literals::string_literals;
using i64 = std::int_fast64_t;
using std::cout;
using std::cerr;
using std::endl;
using std::cin;

#if defined(DONLINE_JUDGE)
	#define NDEBUG
#elif defined(ONLINE_JUDGE)
	#define NDEBUG
#endif

template<typename T> std::vector<T> make_v(size_t a){return std::vector<T>(a);}
template<typename T, typename... Ts> auto make_v(size_t a, Ts... ts){
  return std::vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

int main() {
	int w, z; double b; scanf("%d%d%lf", &w, &z, &b);

	printf("%d\n", (int)std::round((double)(w + z) * (b + 1)));
	return 0;
}