Thread: How to make greatest 3 digit number from given number

please help me i m making program which takes a number from user and then make greates 3 digit number from the digits of that number
ex. if user type 57149 then output should be 975 because this is the greatest number that can be formed by digits. i tried below code but when i type number nothing is shown

Code:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a[20],n,no,i,cnt=0;
    printf("Enter a no.");
    scanf("%d",&no);
    n=no;
    while(no!=0)
    {
        no=n/10;
        cnt++;
    }
            for(i=0;i<cnt;i++)
            {
                a[i]=n%10;
                n=n/10;
                if(n==0)
                break;
            }
    for(i=0;i<cnt;i++)
    printf("%d\n",a[i]);
    return 0;
}

above program even not printing the digits of number. so i didnt type further but once i get code to separate digits i will sort the array and will print first 3 numbers because we want 3 digit largest number
but first someone correct this code so it can separate digits please help me
thanks