#include <stdio.h>
int main()
{
    int n, m;
    scanf("%d%d",&n,&m);
    char s[51];
    for (int i = 0;i < n;i++) {
        scanf("%s",&s);
        for (int j = 0;j < m - 3;j++) {
            if (s[j] == 'L' && s[j + 1] == 'O' && s[j + 2] == 'V' && s[j + 3] == 'E') {
                puts("YES");
                return 0;
            }
        }
    }
    puts("NO");
}