#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long n;
  cin >> n;
  long long size = 0, nn = n;
  while (nn) {
    size++;
    nn /= 10;
  }
  if (!(size & 1)) {
    long long lim = 1 << size;
    for (long long i = 0; i < lim; i++) {
      if (__builtin_popcount(i) != size / 2) continue;
      long long num = 0, pow = 1, mask = 1, j = 1;
      while (j <= size) {
        if (i & mask)
          num += (pow * 7);
        else
          num += (pow * 4);
        pow *= 10;
        mask = mask << 1;
        j++;
      }
      if (num >= n) {
        cout << num;
        return 0;
      }
    }
  }
  size = (size & 1) ? size + 1 : size + 2;
  for (long long i = 1; i <= size / 2; i++) cout << 4;
  for (long long i = 1; i <= size / 2; i++) cout << 7;
}
