백준 1032번 C++

#include <iostream>
#include <string>

using namespace std;
const int MAX = 51;

int main(void) {
	int n;
	string str[MAX];

	cin >> n;
	for (int i = 0; i < n; i++)
		cin >> str[i];

	for (int i = 0; i < str[0].length(); i++) {
		for (int j = 1; j < n; j++) {
			if (str[0][i] != str[j][i]) {
				str[0][i] = '?';
				break;
			}
		}
		cout << str[0][i];
	}
	cout << endl;
	return 0;
}