#include <bits/stdc++.h>
using namespace std;
char a[100005];
int cnt[1000] = {};
int main() {
  cin >> a;
  int n = strlen(a), tot = 0;
  for (int i = 0; i < n; i++)
    if (cnt[a[i]]++ == 0) tot++;
  if (tot > 4) return 0 * printf("No\n");
  if (tot == 4) return 0 * printf("Yes\n");
  if (tot == 3) {
    bool flag = 0;
    for (int i = 'a'; i <= 'z'; i++)
      if (cnt[i] > 1) flag = 1;
    if (flag)
      return 0 * printf("Yes\n");
    else
      return 0 * printf("No\n");
  }
  if (tot == 2) {
    int flag = 0;
    for (int i = 'a'; i <= 'z'; i++)
      if (cnt[i] > 1) flag++;
    if (flag == 2)
      return 0 * printf("Yes\n");
    else
      return 0 * printf("No\n");
  }
  printf("No\n");
  return 0;
}
