#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
ll N = 1e9+7;
ll oo =1e13;
const ll maxx = 1000000 + 3;
ll n,m,k,q,x,y,z,l,r,mid,ans;

void go(ll num){
    //4 ,7 ,44,47,74,77
}
void solve() {
    cin>>n;

    ll j=0;
    vector<ll>v={4,7};
    for (ll i =0;i<10;i++) {
        for (;j<v.size();j++) {
            if (v[j]>1e9)break;
            v.push_back(v[j]*10+4);
            v.push_back(v[j]*10+7);
        }
    }
    vector<ll>v2;
    for (ll i =0;i <v.size();i++) {
        ll num=v[i];
        ll f=0,s=0;
        while (num>0) {
            if (num%10==4)f++;
            else s++;
            num/=10;
        }
        if (f==s) v2.push_back(v[i]);
    }
    cout<<*lower_bound(v2.begin(),v2.end(),n);
}
int main() {
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    ll t=1 ;
    // cin >>t;
    while (t--) {
        ans=0;
        solve();
    }
}