#include <iostream>
using namespace std;
int main(){
    int n,m;char str[51];
    bool found=false;
    cin >> n >> m;
    for(int i=0;i<n;i++){
        cin >> str;
        for(int k=0;k+3<m;k++){
            if(str[k+0]=='L')
            if(str[k+1]=='O')
            if(str[k+2]=='V')
            if(str[k+3]=='E')found=true;
        }
    }
    if(found)cout << "YES" << endl; 
    else cout << "NO" <<endl;
    return 0;
}