L题wa了求大佬帮忙看看问题所在

#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 10, INF = 0x3f3f3f3f , M=1e9+7;
#define pb push_back
#define PII pair<int,int>
#define	int long long 
int n;
string s;
void solve(){
	cin>>n>>s;
	if(n<7)
	{
		cout<<"NO"<<endl;
		return;
	}
	string t="CHICKEN";
	if(n==7)
	{
		if(s!=t)
		{
			cout<<"NO"<<endl;
			return;
		}
		else
		{
			cout<<"YES"<<endl;
			return;
		}
	}
    if(n%2==0)
	{
        cout<<"NO"<<endl;
        return;
	}
	int i,j;
	i=j=0;
	vector<int>a;
	map<char,int>mp;
	while(i<n)
	{
		if(j<7&&s[i]==t[j])
		{
			i++;
			j++;
		}
		else
		{
			mp[s[i]]++;
			i++;
		}
	}
	if(j!=7)cout<<"NO"<<endl;
	else 
	{
		for(pair<char,int> p:mp){
			a.pb(p.second);
		}
		sort(a.begin(),a.end());
		int si=a.size();
		int sum=a[si-1];
		for(int i=a.size()-2;i>=0;i--)
        {
            sum=abs(sum-a[i]);
        }
        if(sum!=0)cout<<"NO"<<endl;
        else cout<<"YES"<<endl;
	}	
}
signed main(){

   ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int T = 1;
   cin >> T;
    while (T--) 
	{
		solve();
	}
    return 0;
}