#include <bits/stdc++.h>
#include <atcoder/modint>

using mint = atcoder::modint998244353;

const mint INV2 = mint{2}.inv();

mint count(long k, long n, long a) {
	long cur = n, res = 0;

	while(cur > k) {
		if(cur % a == 0 && cur / a >= k) cur /= a, ++res;
		else {
			long take = cur % a;
			cur -= take, res += take;
		}
	}

	return res;
}

mint solve(long n, long a) {
	mint res = 0;
	
	if(a == 1) {
		return mint{ n } * mint{ n - 1 } * INV2;
	}

	std::vector<long> sp = { n };
	while(sp.back() > 0) {
		auto next = sp.back() / a;
		sp.push_back(next);
	}
	std::ranges::reverse(sp);

	auto p = sp.size();
	
	for(int i : std::views::iota(1uz, p)) {
		mint base = count(sp[i], n, a);
		mint len = sp[i] - sp[i - 1];
		
		// std::cerr << i << ": " << sp[i - 1] << ", " << base.val() << ", " << len.val() << "\n";
		
		res += len * (base + (len - 1) * INV2);
	}

	return res;	
}

int main() {
	int t; std::cin >> t;
	for(const auto $ : std::views::iota(0, t)) {
		long n, a; std::cin >> n >> a;
		std::cout << solve(n, a).val() << "\n";
	}
}