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

#define rep(i, a, b) for (ll i = a; i < b; i++)
using ll = long long;

int main(){
    int n, a, b;
    cin >> n >> a >> b;
    int ans = 0;
    rep(i, 1, n + 1) {
        if(i % a > i % b) ans++;
    }
    cout << ans << endl;
}