#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int main(void){
int n,m;scanf("%d %d",&n,&m);
char s[500];
for(int i=0;i<n;i++){
scanf("%s",s);
    for(int j=0;s[j+3]!='\0';j++){
        if(s[j]=='L'&&s[j+1]=='O'&&s[j+2]=='V'&&s[j+3]=='E'){printf("YES\n");return 0;}
    }
}

printf("NO\n");
}