C program to perform difference operation on sets

Difference of Sets:- If there are two sets A and B, then the difference of two sets A and B is equal to the set which consists of elements present in A but not in B. It is represented by A-B.
Example:- If A = {1,2,3,4,5,6,7} and B = {6,7} are two sets. Then, the difference of set A and set B is given by; A – B = {1,2,3,4,5}

 // write a program in c to create two set and
 // perform the difference  Operation on sets
 #include<stdio.h>
 #include<conio.h>
 int a[20],b[20],c[20],d[20],i,j,k=0,n,m,flag=0;
 void difference()
 {
    printf("\nA-B\n");
    for(i=0;i<n;i++)
    {
        flag=0;
        for(j=0;j<m;j++)
        {
            if(a[i]==b[j])
            {
                flag=1;
                break;
            }
        }
        if(flag==0)
        {
            printf("%d  ",a[i]);
        }
    }
    printf("\n\nB-A\n");
    for(i=0;i<m;i++)
    {
        flag=0;
        for(j=0;j<n;j++)
        {
            if(b[i]==a[j])
            {
                flag=1;
                break;
            }
        }
        if(flag==0)
        {
            printf("%d  ",b[i]);
        }
    }
 }
 int main()
 {
    // create first set A
    printf("Enter the size of first set A:-\n");
    scanf("%d",&n);
    printf("Enter the element of set A:-\n");
    for(i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
    }
    //creating second set B
    printf("Enter the size of second set B:-\n");
    scanf("%d",&m);
    printf("Enter the element of B:-\n");
    for(i=0;i<m;i++)
    {
        scanf("%d",&b[i]);
    }
    
    printf("\n set A is :-\n");
    for(i=0; i<n;i++)
    {
        printf("%d ", a[i]);
    }
    printf("\n set B is :-\n");
    for(i=0; i<m;i++)
    {
        printf("%d ", b[i]);
    }
    printf("\n diffrence of sets is :-\n");
    difference();
    printf("\n");
    getch();
  }

When the above program is executed, it produces following results --

  Enter the size of second set A:-
  7
  Enter the element of set A:-
  12
  65
  9
  4
  71
  90
  33
  Enter the size of second set B:-
  5
  Enter the element of B:-
  34 
  12
  75
  65
  4
  
   set A is :-
  12 65 9 4 71 90 33 
   set B is :-
  34 12 75 65 4 
  diffrence of sets is :-
  
  A-B
  9  71  90  33  
  
  B-A
  34  75