###### tags: `(Zero Judge)`
# b523. 先別管這個了，你聽過安麗嗎？
### 原cin40%

#include<bits/stdc++.h>
using namespace std;

int main()
{
	int b,i;
	vector<string> word;
	string a;
	while(cin>>a)
	{
		b=0;
		word.push_back(a);
		for(i=0;i<word.size()-1;i++)
		{
			if(a==word.at(i))
			{
				b=1;
			}
		}
		if(b==0)
		cout<<"NO"<<endl;
		else
		cout<<"YES"<<endl;
	}
}

### getline(x,y) 100%

#include<bits/stdc++.h>
using namespace std;

int main()
{
	int b,i;
	vector<string> word;
	string a;
	while(getline(cin,a))
	{
		b=0;
		word.push_back(a);
		for(i=0;i<word.size()-1;i++)
		{
			if(a==word.at(i))
			{
				b=1;
			}
		}
		if(b==0)
		cout<<"NO"<<endl;
		else
		cout<<"YES"<<endl;
	}
}