#include <bits/stdc++.h>
using namespace std;
string s, t;
int l[200005], r[200005], last[200005];
int main() {
  cin >> s >> t;
  memset(last, -1, sizeof(last));
  int j = 0, slen = s.size(), tlen = t.size();
  for (int i = 0; i < slen; i++) {
    l[i] = last[s[i] - 'a'];
    if (j < tlen && s[i] == t[j]) {
      l[i] = j;
      j++;
    }
    last[s[i] - 'a'] = l[i];
  }
  memset(last, -1, sizeof(last));
  j = tlen - 1;
  for (int i = slen - 1; i >= 0; i--) {
    r[i] = last[s[i] - 'a'];
    if (j >= 0 && s[i] == t[j]) {
      r[i] = j;
      j--;
    }
    last[s[i] - 'a'] = r[i];
  }
  bool ok = true;
  for (int i = 0; i < slen; i++) {
    if (l[i] == -1 || r[i] == -1 || l[i] < r[i]) {
      ok = false;
      break;
    }
  }
  if (ok)
    cout << "yes" << endl;
  else
    cout << "no" << endl;
  return 0;
}
