Problem:
Score : 100 points

Problem Statement

You are given four digits N_1, N_2, N_3 and N_4. Determine if these can be arranged into the sequence of digits "1974".

Constraints

0 \leq N_1, N_2, N_3, N_4 \leq 9

N_1, N_2, N_3 and N_4 are integers.

Input

Input is given from Standard Input in the following format:

N_1 N_2 N_3 N_4

Output

If N_1, N_2, N_3 and N_4 can be arranged into the sequence of digits "1974", print YES; if they cannot, print NO.

Sample Input 1

1 7 9 4

Sample Output 1

YES

We can get 1974 by swapping N_2 and N_3.

Sample Input 2

1 9 7 4

Sample Output 2

YES

We already have 1974 before doing anything.

Sample Input 3

1 2 9 1

Sample Output 3

NO

Sample Input 4

4 9 0 8

Sample Output 4

NO

Solution in C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int main()
{
    int n[4],i,j,hold;
    for(i=0;i<4;i++){
        scanf("%d",&n[i]);
    }
    for(i=3;i>0;i--){
        for(j=0;j<i;j++){
            if(n[j]>n[j+1]){
                hold = n[j];
                n[j] = n[j+1];
                n[j+1] = hold;
            }
        }
    }
    if(n[0]==1 && n[1]==4 && n[2]==7 && n[3]==9 ) printf("YES\n");
    else printf("NO\n");
    return 0;
}