#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, count = 0, q = 0;
  long long ans = 9999999999999;
  cin >> n;
  q = n;
  while (q) {
    q /= 10;
    count++;
  }
  if (count & 1) {
    for (int i = 0; i < count / 2 + 1; i++) cout << '4';
    for (int i = 0; i < count / 2 + 1; i++) cout << '7';
    return 0;
  }
  for (int i = 0; i < (1 << (count + 3)); i++) {
    long long res = 0, q4 = 0, q7 = 0;
    for (int j = 0; j < count + 2; j++) {
      if ((1 << j) > i && res >= n) break;
      res *= 10;
      if (i & (1 << j)) {
        res += 4;
        q4++;
      } else {
        res += 7;
        q7++;
      }
    }
    if (q4 == q7 && res >= n && res < ans) ans = res;
  }
  cout << ans;
  return 0;
}
