#include<iostream>
#include<vector>
#include<string>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)

int main(void)
{
    int n,m;
    cin>>n>>m;
    vector<string> s(n);
    rep(i,n)
    {
        cin>>s[i];
        rep(j,m-3)
        {
            if(s[i][j]=='L' && s[i][j+1]=='O' && s[i][j+2]=='V' && s[i][j+3]=='E')
            {
                cout << "YES" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
    return 0;
}