#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<unsigned long long> v;
  char x2[] = "47";
  do {
    v.push_back(stoi(x2));
  } while (next_permutation(x2, x2 + 2));
  char x4[] = "4477";
  do {
    v.push_back(stoi(x4));
  } while (next_permutation(x4, x4 + 4));
  char x6[] = "444777";
  do {
    v.push_back(stoi(x6));
  } while (next_permutation(x6, x6 + 6));
  char x8[] = "44447777";
  do {
    v.push_back(stoi(x8));
  } while (next_permutation(x8, x8 + 8));
  v.push_back(4444477777);
  sort(v.begin(), v.end());
  string s;
  cin >> s;
  unsigned long long q = stoi(s);
  if (q <= v[0]) {
    cout << v[0];
    return 0;
  } else
    for (int i = 0; i < v.size() - 1; i++)
      if (q == v[i + 1] || (q > v[i] && q < v[i + 1])) {
        cout << v[i + 1];
        return 0;
      }
  cout << v[98];
  return 0;
}
