#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const long long mxn = 1e9 + 7;
const long long inf = 1e18;
vector<long long> vec;
void fun(long long n, long long four, long long seven) {
  if (n > mxn) {
    return;
  }
  long long tem1 = (10 * n) + 4;
  if ((four + 1) == seven) {
    vec.push_back(tem1);
  }
  fun(tem1, four + 1, seven);
  long long tem2 = (10 * n) + 7;
  if (four == (seven + 1)) {
    vec.push_back(tem2);
  }
  fun(tem2, four, seven + 1);
  return;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  long long i, j, k, a, b, c, d, n, m, t, u, v, w, x, y, z;
  cin >> n;
  fun(0, 0, 0);
  sort(vec.begin(), vec.end());
  long long pos = lower_bound(vec.begin(), vec.end(), n) - vec.begin();
  long long ans = vec[pos];
  cout << ans << "\n";
  return 0;
}
