#include <bits/stdc++.h>
using namespace std;
long long a[101] = {
    0,        47,       74,       4477,     4747,     4774,     7447,
    7474,     7744,     444777,   447477,   447747,   447774,   474477,
    474747,   474774,   477447,   477474,   477744,   744477,   744747,
    744774,   747447,   747474,   747744,   774447,   774474,   774744,
    777444,   44447777, 44474777, 44477477, 44477747, 44477774, 44744777,
    44747477, 44747747, 44747774, 44774477, 44774747, 44774774, 44777447,
    44777474, 44777744, 47444777, 47447477, 47447747, 47447774, 47474477,
    47474747, 47474774, 47477447, 47477474, 47477744, 47744477, 47744747,
    47744774, 47747447, 47747474, 47747744, 47774447, 47774474, 47774744,
    47777444, 74444777, 74447477, 74447747, 74447774, 74474477, 74474747,
    74474774, 74477447, 74477474, 74477744, 74744477, 74744747, 74744774,
    74747447, 74747474, 74747744, 74774447, 74774474, 74774744, 74777444,
    77444477, 77444747, 77444774, 77447447, 77447474, 77447744, 77474447,
    77474474, 77474744, 77477444, 77744447, 77744474, 77744744, 77747444,
    77774444};
long long n;
int main() {
  scanf("%I64d", &n);
  if (n >= 77777777) {
    printf("4444477777");
    return 0;
  }
  for (int i = 0; i < 100; i++) {
    if (a[i] >= n) {
      printf("%I64d", a[i]);
      return 0;
    }
  }
  return 0;
}
