#include <bits/stdc++.h>
using namespace std;
long long n, n1, n2, mini, mini2;
bool f, f2;
void countfour(long long t1) {
  int c4 = 0, c7 = 0;
  if (f && mini < t1) return;
  string s = to_string(t1);
  for (int i = 0; i < s.size(); ++i) {
    if (s[i] == '4')
      c4++;
    else
      c7++;
  }
  if (s.size() % 2 == 0 && (abs(c4 - c7) >= 1) && t1 >= n) return;
  if (s.size() % 2 == 0 && (c4 == 0 || c7 == 0) && t1 >= n) return;
  if (t1 >= n && c4 == c7 && mini > t1) {
    mini = t1;
    n1 = t1;
    f = 1;
    return;
  }
  countfour((t1 * 10) + 4);
  countfour((t1 * 10) + 7);
}
void countseven(long long t2) {
  int c4 = 0, c7 = 0;
  if (f2 && mini2 < t2) return;
  string s = to_string(t2);
  for (int i = 0; i < s.size(); ++i) {
    if (s[i] == '4')
      c4++;
    else
      c7++;
  }
  if (s.size() % 2 == 0 && (abs(c4 - c7) >= 1) && t2 >= n) return;
  if (s.size() % 2 == 0 && (c4 == 0 || c7 == 0) && t2 >= n) return;
  if (t2 >= n && c4 == c7 && mini2 > t2) {
    mini2 = t2;
    n2 = t2;
    f2 = 1;
    return;
  }
  countseven((t2 * 10) + 4);
  countseven((t2 * 10) + 7);
}
int main() {
  cin >> n;
  mini = mini2 = 999999999999;
  f = f2 = 0;
  countfour(4);
  countseven(7);
  if (n1 == 0)
    cout << n2 << endl;
  else if (n2 == 0)
    cout << n1 << endl;
  else {
    cout << min(n1, n2) << endl;
  }
  return 0;
}
