#include <bits/stdc++.h>
using namespace std;
#define ll  long long
#define SZ(v)   (int((v).size()))
#define pb  push_back
vector<ll> lucky;
void pre_calc (ll num) {
    if (num > 1e10)
        return;
    lucky.pb(num);
    pre_calc((num * 10) + 7);
    pre_calc((num * 10) + 4);
}
void run () {
    int n;
    cin >> n;
    pre_calc(0);
    sort(lucky.begin(), lucky.end());
    for (int i = 0; i < SZ(lucky); ++i) {
        if (lucky[i] >= n) {
            int four, seven;
            four = seven = 0;
            ll cur = lucky[i];
            while (cur) {
                if (cur % 10 == 4)
                    four++;
                else
                    seven++;
                cur /= 10;
            }
            if (four == seven) {
                cout << lucky[i] << '\n';
                return;
            }
        }
    }
}
int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
//    freopen("/home/hamoudi/clion/hello.in", "rt", stdin);
    int tt;
    tt = 1;
//    cin >> tt;
    while (tt--)
        run();
}