有个问题？

#include <iostream>
using namespace std;

const unsigned long long mod = 998244353;

int main() {
	unsigned long long n;
	cin >> n;

	unsigned long long q = n / mod;  // 商
	unsigned long long r = n % mod;  // 余数
	cout << (q * r) % mod << endl;
	return 0;
}

unsigned long long r = n % mod + 1 % mod;