/* -*- coding: utf-8 -*-
 *
 * 3773.cc:  No.3773 mod A > mod B - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* main */

int main() {
  int n, a, b;
  scanf("%d%d%d", &n, &a, &b);

  int cnt = 0;
  for (int i = 1; i <= n; i++)
    if (i % a > i % b) cnt++;

  printf("%d\n", cnt);
  
  return 0;
}