怎么看都没看出来啊

#include <iostream>

using namespace std;

int main() {
	int n, uprlmt = 1e9, lwrlmt = 1, curr;
	while (true) {
		curr = (uprlmt + lwrlmt) / 2;
		cout << curr << endl;
		cin >> n; 
		if (curr == uprlmt - 1 and n == 1) {
			cout << uprlmt;
			return 0;
		}
		if (n == 0) {
			return 0;
		}
		(n == -1 ? lwrlmt : uprlmt) = curr;
	}
}