#include <stdio.h>
int main(void){
	int tate, yoko;
	scanf("%d%d",&tate,&yoko);
	
	char str[yoko];
	for(int i = 0;i < tate;i ++){
		scanf("%s",str);
		for(int j = 0;j < yoko;j ++){
			if(str[j] == 'L' && str[j + 1] == 'O' && str[j + 2] == 'V' && str[j + 3] == 'E'){
				printf("YES");
				return 0;
			}
		}
	}
	printf("NO");
}