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

long long n, a, b;

int main() {
	cin >> n >> a >> b;

	if (2 * a > b)
		cout << -a * (n - 1) - b * (n - (n - 1) / 2 * 2);
	else
		cout << a * (n - 1) - b * n;
}