#include <iostream>
#include <vector>
#include <map>
#include<string>
#include<queue>
#include<math.h>
#define all(x) begin(x),end(x)
#define ll long long
#define P pair<int,int>
#define lP pait<ll,ll>
using namespace std;
int main() {
    bool f=0;
    int n,m;
    cin>>n>>m;
    for(int i=0;i<n;i++){
        string s;
        cin>>s;
        for(int i=0;i<m-3;i++){
            if(s[i]=='L' and s[i+1]=='O' and s[i+2]=='V' and s[i+3]=='E') f=1;
        }
    }
    if(f) cout<<"YES"<<endl;
    else cout<<"NO"<<endl;
    return 0;
}