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

long long n, a, b;

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

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