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

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N,a,b; cin >> N >> a >> b;
    int answer = 0;
    for(int i=1; i<=N; i++) answer += (i%a)>(i%b);
    cout << answer << endl; 
}