大佬帮忙看看出了什么问题

#include <iostream>

using namespace std;

long long n;
long long prea[2000005];
int main() {
	//ios::sync_with_stdio(0);
	//cin.tie(0);
	cin >> n;
	int cnt = 0;
	while(1) {
		prea[++cnt] = prea[cnt - 1] + cnt;
		if(cnt >= 2000000) break;
	}
	int l = 0, r = 0;
	while(l <= n && r <= n) {
		if(prea[r] - prea[l] == n) {
			if(l + 1 != r)cout << l + 1 << " " << r << endl;
			l++;
		}
		if(prea[r] - prea[l] < n) {
			r++;
		}
		if(prea[r] - prea[l] > n) {
			l++;
		}
	}
	return 0;
}