18301.cpp

// 18301. Rats
// 2020.12.12
// 입문용, 사칙연산
#include<iostream>

using namespace std;

int main()
{
    int a, b, c;
    cin >> a >> b >> c;
    cout << (a + 1) * (b + 1) / (c + 1) - 1 << endl;
    return 0;
}