#include <bits/stdc++.h>
#define REP(i,n) for(int i=0; i<(n); i++)
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
int main()
{
	string S;
	vector<string> str;
	while( getline( cin, S ) )
	{
		string tmp;
		tmp += S[0];
		tmp += S[2];
		tmp += S[4];
		str.push_back( tmp );
	}
	REP( i, (int)str.size() - 1 )
	{
		if( str[ i ] < str[ i + 1 ] )
		{
			cout << "NO" << endl;
			return 0;
		}
	}
	cout << "YES" << endl;
	return 0;
}