#include <iostream>
#include <cmath>
#include <cstring>
#include <string>
#include <set>
#include <vector>
#include <algorithm>
#define ll long long
#define INF 1e9
using namespace std;
bool contain47(int n) {
	int flag = 1;
	while(n) {
		if(n % 10 != 4 && n % 10 != 7) {
			flag = 0;
			break;
		} 
		n /= 10;
	}
	return flag;
}
int getW4(int n) {
	int res = 0;
	while(n) {
		if(n % 10 == 4)
			res++;
		n /= 10;
	}
	return res;
}
int getW7(int n) {
	int res = 0;
	while(n) {
		if(n % 10 == 7)
			res++;
		n /= 10;
	}
	return res;
}
int nw(int n) {
	int res = 0;
	while(n) {
		n /= 10;
		res++;
	}
	return res;
}
int a[] = {47,74,4477,4747,4774,7447,7474,7744,444777,447477,447747,447774,474477,474747,474774,477447,477474,477744,744477,744747,744774,747447,747474,747744,774447,774474,774744,777444,44447777,44474777,44477477,44477747,44477774,44744777,44747477,44747747,44747774,44774477,44774747,44774774,44777447,44777474,44777744,47444777,47447477,47447747,47447774,47474477,47474747,47474774,47477447,47477474,47477744,47744477,47744747,47744774,47747447,47747474,47747744,47774447,47774474,47774744,47777444,74444777,74447477,74447747,74447774,74474477,74474747,74474774,74477447,74477474,74477744,74744477,74744747,74744774,74747447,74747474,74747744,74774447,74774474,74774744,74777444,77444477,77444747,77444774,77447447,77447474,77447744,77474447,77474474,77474744,77477444,77744447,77744474,77744744,77747444,77774444};
int main() {
	ios::sync_with_stdio(false); cin.tie(0);
	int n;
	cin >> n;
	/*
	//打表 
	for(int i = 1; i <= INF; ++i) {
		if(contain47(i) && getW4(i) == getW7(i) && ((getW4(i) + getW7(i)) % 2 == 0)) {
			cout << i << ",";
		}	
	}
	*/
	int size = sizeof(a) / sizeof(int);
	for(int i = 0; i < size; ++i) {
		if(a[i] >= n) {
			cout << a[i];
			break;
		}
	}
	return 0;
}