解法：

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main() {
	int n;
	cin >> n;
	vector<int> arr(n);
	vector<int> tong(1000);
	for (auto& x : arr) {
		cin >> x;
		tong[x]++;
	}
	int p=max_element(tong.begin(), tong.end()) - tong.begin();
	if (tong[p] > n / 2) {
		cout << p;
	}
	else cout << -1;
	return 0;
}