#include <bits/stdc++.h>
using namespace std;
const long long MAXN = 1010, INF = 100000000000;
long long a[100], n, k, ans = INF;
void check() {
  long long res = 0, p = 1, k1 = 0, k2 = 0;
  for (int i = 0; i < k; i++) {
    res = res * 10 + a[i];
    k1 += (a[i] == 4);
    k2 += (a[i] == 7);
  }
  if (k1 == k2 && res >= n && res < ans) ans = res;
}
void calc(int p) {
  for (int i = 4; p < k && i <= 7; i += 3) {
    a[p] = i;
    if (p + 1 == k)
      check();
    else
      calc(p + 1);
  }
}
int main() {
  cin >> n;
  for (k = 1; k <= 10; k++) calc(0);
  cout << ans;
  return 0;
}
