#include <stdio.h>
#include <string.h>

int main(void)
{
	int n, m;
	char s[50][51];
	int judge = 0;
	int i, j;

	scanf("%d %d", &n, &m);

	for (i = 0; i < n; i++) {
		scanf("%s", &s[i]);
	}
	
	for (i = 0; i < n; i++) {
		for (j = 0; j < strlen(s[i]) - 3; j++) {
			if (s[i][j] == 'L' && s[i][j + 1] == 'O' && s[i][j + 2] == 'V' && s[i][j + 3] == 'E') {
				judge = 1;
				goto print;
			}
		}
	}

print:		
	printf("%s\n", judge ? "YES" : "NO");

	return 0;
}