#include <iostream>
#include <algorithm>
#include <vector>
#include <string>

using namespace std;

long long n, c, v;

long long f(int len, int clip) {
  if (len >= n) return 0;
  clip = len;
  long long ret = (n - len + clip - 1) / clip;
  for (int i = 1; i < 20; i++) {
    ret = min(ret, f(len + clip * i, clip) + v * i);
  }
  return ret + c;
}

int main() {
  cin >> n >> c >> v;
  cout << f(1, 0) << endl;
}