#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include <string.h>

int main()
{
	char fossilVer[6] = "";
	char assessVer[6] = "";

	scanf("%s", fossilVer);
	scanf("%s", assessVer);

	for (int i = 0;assessVer[i] != '\0';)
	{
		if (fossilVer[i] == assessVer[i])
		{
			i += 2;
		}
		else if (fossilVer[i] > assessVer[i])
		{
			printf("YES\n");
			return 0;
		}
		else
		{
			printf("NO\n");
			return 0;
		}
	}

	printf("NO\n");
	return 0;
}