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

int main() {
    int N, A, B, cnt = 0;
    cin >> N >> A >> B;
    for (int n = 1; n <= N; n++) {
        if ((n % A) > (n % B)) {
            cnt++;
        }
    }
    cout << cnt << endl;
    return 0;
}