## Algorithm

B. Lucky Numbers (easy)
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

Petya loves lucky numbers. Everybody knows that positive integers are lucky if their decimal representation doesn't contain digits other than 4 and 7. For example, numbers 477444 are lucky and 517467 are not.

Lucky number is super lucky if it's decimal representation contains equal amount of digits 4 and 7. For example, numbers 477744474477 are super lucky and 4744467 are not.

One day Petya came across a positive integer n. Help him to find the least super lucky number which is not less than n.

Input

The only line contains a positive integer n (1 ≤ n ≤ 109). This number doesn't have leading zeroes.

Output

Output the least super lucky number that is more than or equal to n.

Please, do not use the %lld specificator to read or write 64-bit integers in C++. It is preferred to use the cin, cout streams or the %I64d specificator.

Examples
input
Copy
`4500`
output
Copy
`4747`
input
Copy
`47`
output
Copy
`47`

## Code Examples

### #1 Code Example with C++ Programming

```Code - C++ Programming```

``````#include <iostream>
#include  <queue>

using namespace std;

struct SuperLucky {
long long number;
int fours, sevens;
};

void bfs(int des) {
queue <SuperLucky> q;
SuperLucky tmp;

tmp.number = 4;
tmp.fours = 1;
tmp.sevens = 0;
q.push(tmp);

tmp.number = 7;
tmp.fours = 0;
tmp.sevens = 1;
q.push(tmp);

while (!q.empty()) {
int size = q.size();

while (size--) {
SuperLucky fr = q.front();
q.pop();

fr.number *= 10;
fr.number += 4;
fr.fours++;

if (fr.number >= des && fr.fours == fr.sevens) {
cout  < < fr.number  < < endl;
return;
}

q.push(fr);

fr.number += 3;
fr.fours--;
fr.sevens++;

if (fr.number >= des && fr.fours == fr.sevens) {
cout  < < fr.number  < < endl;
return;
}

q.push(fr);
}
}
}

int main() {
int des;
cin >> des;
bfs(des);

return 0;
}``````
Copy The Code &

Input

cmd
4500

Output

cmd
4747
Advertisements

## Demonstration

Codeforcess Solution  Lucky Numbers (easy), B. Lucky Numbers (easy) C,C++, Java, Js and Python ,ucky Numbers (easy),Codeforcess Solution