D.cpp

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

int m, a, b;
typedef long long ll;

int cnt = 0;
ll ans = 0;

int mx = 0;
const int MAXN = 100100;
bool vis[MAXN];
void bfs() {
  int cur = 0;
  while (!vis[cur]) {
    vis[cur] = true;
    if (cur > m) {
      ans += ll(m - mx) * cnt;
      break;
    }
    if (cur > mx) {
      ans += ll(cur - mx) * cnt;
      mx = cur;
    }
    ++cnt;
    if (cur >= b) cur -= b;
    else cur += a;
  }
}

int gg(int a, int b) {
  if (a == 0) return b;
  return gg(b % a, a);
}

int main() {
  cin >> m >> a >> b;
  bfs();
  int g = gg(a, b);
  for(int i = 0; i < a; i += g) {
    ll first = mx - mx % a + i;
    if (first < mx) first += a;
    ll last = m - m % a + i;
    if (last > m) last -= a;
    ll lo = first / a + 1;
    ll hi = last / a;
    ans += (lo - 1) * (first - mx); // [mx, first): lo - 1
    ans += a * ((lo + hi) * (hi - lo + 1)) / 2; // [first, last): lo...hi
    ans += (m - last + 1) * hi; // [last, m]: hi+1
  }
  cout << ans << "\n";
}