就第一个测试点死活通过不了，感觉逻辑上没啥问题啊(ToT)/~~~

#include <iostream>

using namespace std;

int main()
{
	int n = 0; cin >> n;
	
	char word = 0, letter = 0;
	
	while(cin >> word)
	{
		static int cnt = 0;
		
		if(word != letter)
		{
			letter = word;
			cnt = 1;
		}
		else
		{
			if(++cnt >= n)
			{
				cout << letter << endl;
				
				return 0;	
			} 
		}
	}
	
	cout << "NO" << endl;
	
	return 0;
}