#include <stdio.h>
#include <stdlib.h>

int main()
{
	int n, m, flag = 0;
	char** s;

	if (scanf("%d %d", &n, &m) != 2) {
		return -1;
	}

	s = (char**)malloc(sizeof(char*) * n);

	if (s == NULL) {
		return -1;
	}

	for (int i = 0; i < n; i++) {
		*(s + i) = (char*)malloc(sizeof(char) * m + 1);

		if (scanf("%s", *(s + i)) != 1) {
			return -1;
		}

		if (*(s + i) == NULL) {
			return -1;
		}
	}

	if (m > 3) {
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m - 3; j++) {
				if (*(*(s + i) + j + 0) == 'L' &&
					*(*(s + i) + j + 1) == 'O' &&
					*(*(s + i) + j + 2) == 'V' &&
					*(*(s + i) + j + 3) == 'E') {
					flag = 1;
					break;
				}
			}

			if (flag == 1) {
				break;
			}
		}
	}

	if (flag == 1) {
		printf("YES");
	}
	else {
		printf("NO");		
	}

	for (int i = 0; i < n; i++) {
		free(*(s + i));
		*(s + i) = NULL;
	}

	free(s);
	s = NULL;

	return 0;
}