#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n;
  vector<long long int> v;
  string s;
  long long int m = 47, k;
  s = to_string(m);
  stringstream geek(s);
  geek >> k;
  v.push_back(k);
  while (s.size() <= 10) {
    if (next_permutation(s.begin(), s.end())) {
      stringstream geek(s);
      geek >> k;
      v.push_back(k);
    } else {
      s.resize(s.size() + 2);
      for (int i = 0; i < s.size(); i++) {
        if (i < s.size() / 2)
          s[i] = '4';
        else
          s[i] = '7';
      }
      stringstream geek(s);
      geek >> k;
      v.push_back(k);
    }
  }
  cin >> n;
  vector<long long int>::iterator lower = lower_bound(v.begin(), v.end(), n);
  cout << v[lower - v.begin()];
}
