#include <bits/stdc++.h>
using namespace std;
void itval(istream_iterator<string> it) {}
template <typename T, typename... Args>
void itval(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << endl;
  itval(++it, args...);
}
const long long int MOD = 1e9 + 7;
template <typename T>
inline void print(T x) {
  cout << x << "\n";
}
template <typename T>
inline void printvec(T x) {
  for (auto a : x) cout << a << ' ';
  cout << '\n';
}
struct custom {
  bool operator()(const pair<long long int, long long int> &p1,
                  const pair<long long int, long long int> &p2) const {
    if (p1.first == p2.first) return p2.second < p1.second;
    return p1.first < p2.first;
  }
};
long long int get_pow(long long int a, long long int b) {
  long long int res = 1;
  while (b) {
    if (b & 1) res = (res * a) % MOD;
    a = (a * a) % MOD;
    b >>= 1;
  }
  return res;
}
const long long int N = 1e5 + 10, inf = 4e18;
char s[N];
bool dp[N][4];
void solve() {
  scanf("%s", s);
  int n = 0;
  for (int i = 0; 1; i++) {
    if (!s[i]) {
      n = i;
      break;
    }
  }
  dp[n][2] = 1;
  dp[n][3] = 1;
  set<string> ans;
  for (int i = n - 2; i >= 5; i--) {
    for (int j = 2; j <= 3; j++) {
      string a = "", b = "";
      for (int k = i; k < i + j; k++) {
        a.push_back(s[k]);
        b.push_back(s[k + j]);
      }
      if (dp[i + j][j ^ 1] || (dp[i + j][j] && a != b)) {
        dp[i][j] = 1;
        ans.insert(a);
      }
    }
  }
  print(ans.size());
  for (auto p : ans) cout << p << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int test = 1;
  clock_t z = clock();
  for (long long int tes = (long long int)0; tes < (long long int)(test);
       tes++) {
    solve();
  }
  fprintf(stderr, "Total Time:%.4f\n", (double)(clock() - z) / CLOCKS_PER_SEC),
      fflush(stderr);
  return 0;
}
