春联----思维

#include 
#include 
using namespace std;
const int N = 200010;
signed main()
{
	char s[N];
    cin>> s+1;
    int n=strlen(s+1);
    int i=n-1,j=n;
    while(i&&j)
    {
        while(s[j]!=s[i]&&i>0)i--;
        j=i-1;
        if(j<=0||i<=0)break;
        i=j-1;
    }
    if(i<=0)cout<<"kou"<