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: Wrong Answer)

#include<stdio.h>

int main(void){
  int numbers[4] = {}; 
  int i = 0;
  int flag1 = 0;
  int flag9 = 0;
  int flag7 = 0;
  int flag4 = 0;
  
  for(i = 0; i < 4; i++){
  scanf("%d",&numbers[i]);
  if(numbers[i]==1){
    flag1++;
  	}
  if(numbers[i]==9){
    flag9++;
  	}
  if(numbers[i]==7){
    flag7++;
  	}
  if(numbers[i]==4){
    flag4++;
  	}  
  }
  
  if(flag1+flag9+flag7+flag4 == 4)
    printf("YES");
  else
    printf("NO");
}