丑陋的打表+前缀和二分。。。

#include <bits/stdc++.h>

using u32 = unsigned;
using i64 = long long;
using u64 = unsigned long long;
using u128 = unsigned __int128;

int S(i64 x) {
	int res = 0;
	while (x) {
		res += x % 10;
		x /= 10;
	}
	return res;
}

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

	int L, R;
	std::cin >> L >> R;
	std::map<int, int> mp;
	for (i64 i = 1; i <= R; i++) {
		i64 p = i;
		int res = 0;
		while (p % 10 > 3) {
			res++;
			p /= 10;
			p++;
		}
		i = p * std::pow(10, res);
		if (S(i) * S(i) == S(i * i)) {
			mp[i]++;
		}
	}
	int res = 0;
	std::map<int, int> ans;
	std::vector<int> p;
	for (auto [x, y] : mp) {
		p.push_back(x);
		ans[x] = y + res;
		res += y;
	}

	auto l = lower_bound(p.begin(), p.end(), L) - p.begin() - 1;
	auto r = upper_bound(p.begin(), p.end(), R) - p.begin() - 1;

	std::cout << ans[p[r]] - ans[p[l]] << "\n";

	return 0;
}