杜教筛$O(n^{\frac{3}{4}})$
#include <iostream>
#include <cstring>
#include <algorithm>
#define int long long
using namespace std;
const int N = 1e5 + 10;
int s[N];
bool st[N];
int S(int n)
{
if (st[n]) return s[n];
int ans = n * n;
for (int l = 2, r; l <= n; l = r + 1)
{
r = n / (n / l);
ans -= S(n / l) * (r - l + 1);
}
st[n] = true;
return s[n] = ans;
}
signed main()
{
int n, m;
cin >> n >> m;
if (n > m) swap(n, m);
int res = 0;
for (int l = 1, r; l <= n; l = r + 1)
{
r = min(n / (n / l), m / (m / l));
res += (n / l) * (m / l) * (S(r) - S(l - 1));
}
cout << res << endl;
return 0;
}