#include <iostream>
#include <algorithm>
using namespace std;
int N, C, V;
int solve(int n, int c) {
	if (n >= N) return 0;
	int ret = solve(n + c, c) + V;
	if (n > c) ret = min(ret, solve(n, n) + C);
	return ret;
}
int main() {
	cin >> N >> C >> V;
	cout << solve(1, 1) + C << endl;
	return 0;
}