Lucky Sum of Digits.cpp

#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstring>
#include <climits>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
#define REP(i,n) for(int i=0; i<n; i++)
#define FOR(i,st,end) for(int i=st;i<end;i++)
#define db(x) cout << (#x) << " = " << x << endl;
#define mp make_pair
#define pb push_back
#define MAX 10000005
typedef long long int ll;
int main(){
	int n;
	cin>>n;
	if(n<4){
		cout<<"-1";
		return 0;
	}
	int numSeven=n/7;
	int rem=n%7;
	int numFour=rem/4;
	int toBecomeFour=rem%4;
	if(toBecomeFour!=0){
		if(numSeven>=toBecomeFour){
			numFour+=((7*toBecomeFour)+toBecomeFour)/4;
			numSeven-=toBecomeFour;
		}
		else{
			cout<<"-1";
			return 0;
		}
	}
	REP(i,numFour)
		cout<<"4";
	REP(i,numSeven)
		cout<<"7";
}