#include <bits/stdc++.h>
#pragma GCC optimize "trapv"
using namespace std;
vector<string> v;
void printAllKLengthRec(char set[], string prefix, long long int n,
                        long long int k) {
  if (k == 0) {
    if (count(prefix.begin(), prefix.end(), '4') ==
        count(prefix.begin(), prefix.end(), '7'))
      v.push_back(prefix);
    return;
  }
  for (long long int i = 0; i < n; i++) {
    string newPrefix;
    newPrefix = prefix + set[i];
    printAllKLengthRec(set, newPrefix, n, k - 1);
  }
}
void printAllKLength(char set[], long long int k, long long int n) {
  printAllKLengthRec(set, "", n, k);
}
int32_t main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
  ;
  long long int s;
  cin >> s;
  char set[] = {'4', '7'};
  for (long long int i = 2; i <= 10; i += 2) {
    printAllKLength(set, i, 2);
  }
  for (long long int i = 0; i < v.size(); i++) {
    stringstream str(v[i]);
    long long int x = 0;
    str >> x;
    if (x >= s) {
      cout << x;
      break;
    }
  }
  return 0;
}
