我不理解

#include<iostream>
using namespace std;
int cnt,k;
char ch,nowch;
int main()
{
	cin>>k;
	getchar();
	while((ch=getchar())!='\n')
	{
		if(nowch!=ch)
		{
			cnt=1;
			nowch=ch;
		}
		else cnt++;
		if(cnt==k)
		{
			cout<<ch<<endl;
			return 0;
		}
	}
	cout<<"No";
}