#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < (n); ++i)
using namespace std;
int main() {
  int n, m;
  cin >> n >> m;
  string s[n];
  rep(i, n) cin >> s[i];
  bool f = false;
  rep(i, n) {
    rep(j, m - 4) {
      if (s[i][j] == 'L') {
        if (s[i][j + 1] == 'O' && s[i][j + 2] == 'V' && s[i][j + 3] == 'E')
          f = true;
      }
    }
  }
  cout << ((f) ? "YES" : "NO") << endl;
}