#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, const U &b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, const U &b) {
  if (a < b) a = b;
}
template <class T>
inline void gn(T &first) {
  char c, sg = 0;
  while (c = getchar(), (c > '9' || c < '0') && c != '-')
    ;
  for ((c == '-' ? sg = 1, c = getchar() : 0), first = 0; c >= '0' && c <= '9';
       c = getchar())
    first = (first << 1) + (first << 3) + c - '0';
  if (sg) first = -first;
}
template <class T1, class T2>
inline void gn(T1 &x1, T2 &x2) {
  gn(x1), gn(x2);
}
template <class T1, class T2, class T3>
inline void gn(T1 &x1, T2 &x2, T3 &x3) {
  gn(x1, x2), gn(x3);
}
template <class T1, class T2, class T3, class T4>
inline void gn(T1 &x1, T2 &x2, T3 &x3, T4 &x4) {
  gn(x1, x2, x3), gn(x4);
}
template <class T1, class T2, class T3, class T4, class T5>
inline void gn(T1 &x1, T2 &x2, T3 &x3, T4 &x4, T5 &x5) {
  gn(x1, x2, x3, x4), gn(x5);
}
template <class T>
inline void print(T first) {
  if (first < 0) {
    putchar('-');
    return print(-first);
  }
  if (first < 10) {
    putchar('0' + first);
    return;
  }
  print(first / 10);
  putchar(first % 10 + '0');
}
template <class T>
inline void println(T first) {
  print(first);
  putchar('\n');
}
template <class T>
inline void printsp(T first) {
  print(first);
  putchar(' ');
}
template <class T1, class T2>
inline void print(T1 x1, T2 x2) {
  printsp(x1), println(x2);
}
template <class T1, class T2, class T3>
inline void print(T1 x1, T2 x2, T3 x3) {
  printsp(x1), printsp(x2), println(x3);
}
template <class T1, class T2, class T3, class T4>
inline void print(T1 x1, T2 x2, T3 x3, T4 x4) {
  printsp(x1), printsp(x2), printsp(x3), println(x4);
}
template <class T1, class T2, class T3, class T4, class T5>
inline void print(T1 x1, T2 x2, T3 x3, T4 x4, T5 x5) {
  printsp(x1), printsp(x2), printsp(x3), printsp(x4), println(x5);
}
int power(int a, int b, int m, int ans = 1) {
  for (; b; b >>= 1, a = 1LL * a * a % m)
    if (b & 1) ans = 1LL * ans * a % m;
  return ans;
}
char s[10010];
char a[10010];
int dp[10010][10];
vector<string> ans;
string t;
int calc_two(int u) {
  if (u == 1) return 0;
  if (u == 2) return 1;
  if (dp[u - 2][2]) {
    if (a[u - 3] != a[u - 1] || a[u - 2] != a[u]) return 1;
  }
  if (dp[u - 2][3]) return 1;
  return 0;
}
int calc_three(int u) {
  if (u < 3) return 0;
  if (u == 3) return 1;
  if (dp[u - 3][2]) return 1;
  if (dp[u - 3][3]) {
    if (a[u - 5] != a[u - 2] || a[u - 4] != a[u - 1] || a[u - 3] != a[u])
      return 1;
  }
  return 0;
}
int main() {
  scanf("%s", s);
  int n = strlen(s);
  if (n <= 6) {
    puts("0");
    return 0;
  }
  for (int i = 1; i < n - 4; i++) a[i] = s[i + 4];
  n -= 5;
  reverse(a + 1, a + n + 1);
  dp[0][2] = dp[0][3] = 1;
  for (int i = 1; i <= n; i++) {
    dp[i][2] = calc_two(i);
    dp[i][3] = calc_three(i);
  }
  for (int i = 1; i <= n; i++) {
    if (dp[i][2]) {
      t.clear();
      t += a[i];
      t += a[i - 1];
      ans.push_back(t);
    }
    if (dp[i][3]) {
      t.clear();
      t += a[i];
      t += a[i - 1];
      t += a[i - 2];
      ans.push_back(t);
    }
  }
  sort(ans.begin(), ans.end());
  ans.resize(unique(ans.begin(), ans.end()) - ans.begin());
  println(ans.size());
  for (int i = 0; i < ans.size(); i++) cout << ans[i] << endl;
}
