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

using ll = long long;
using db = double;
using bl = bool;
using str = string;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bl>;
using vs = vector<str>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<ll>>;
using pll = pair<ll, ll>;
using pls = pair<ll, str>;
using vpll = vector<pll>;
using vpls = vector<pls>;

#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rrep(i, n) for (ll i = 1; i <= (n); i++)
#define all(v) (v).begin(), (v).end()
#define rall(x) (x).rbegin(), (x).rend()
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define pb push_back
#define eb emplace_back
#define em emplace
#define pob pop_back
#define YES cout << "Yes" << endl
#define NO cout << "No" << endl
#define dame cout << -1 << endl
#define UNIQUE(v) \
    sort(all(v)); \
    v.erase(unique(all(v)), v.end())
#define yn(x) cout << ((x) ? "Yes" : "No") << '\n'
#define fi first
#define se second
#define sz(x) (ll)(x).size()
#define each(x, v) for (auto &x : v)
#define npos str::npos
#define FOUND(s, x) ((s).find(x) != npos)
#define NOT_FOUND(s, x) ((s).find(x) == npos)
#define RANDOM_INIT srand((unsigned)time(NULL)) // rand関数の初期化
#define popcnt(x) __builtin_popcountll(x)

const ll INF = (1LL << 60);
const ll NINF = -(1LL << 60);

template <class T>
istream &operator>>(istream &in, vector<T> &v)
{
    for (T &x : v)
        in >> x;

    return in;
}

int main()
{
    ll n,a,b;
    cin >> n >> a >> b;
    ll cnt = 0;
    rrep(i,n)
    {
        if(i % a > i % b)
        cnt++;
    }
    cout << cnt << endl;
}