two strings is given through the keyboard and fid which one is greater , smaller, or equal and also find their difference . ( string )

#include<stdio.h>
#include<conio.h>
#include<string.h>
main()
{
     char a[20],b[20];
     int i,n;

     printf("enter two string  :\n");
     gets(a);
     gets(b);

    i=0;

    while(a[i]==b[i]&& a[i]!='\0')
  {
     i++;
     n = a[i]-b[i];
  } 

    if(a[i]>b[i])
    printf("a[i] is gerater than b[i] and the difference is %d ",n);

    else if (a[i]<b[i])
    printf("a[i] is smaller than b[i]  and the difference is %d",n);
 

    else if (a[i]-b[i]==0)
    printf("a[i]=b[i]  and the difference is %d",n);


}
output :

enter two string  :
hello
hllo
a[i] is smaller than b[i]  and the difference is -7