Matrix multiplication in c

#include <stdio.h>
 
main()
{
   int m, n, p, q, c, d, k, sum = 0;
   int first[10][10], second[10][10], multiply[10][10];
 
   printf("Enter the number of rows and columns of first matrix\n");
   scanf("%d%d", &m, &n);
   printf("Enter the elements of first matrix\n");
 
   for (  c = 0 ; c < m ; c++ )
      for ( d = 0 ; d < n ; d++ )
         scanf("%d", &first[c][d]);
 
   printf("Enter the number of rows and columns of second matrix\n");
   scanf("%d%d", &p, &q);
 
   if ( n != p )
      printf("Matrices with entered orders can't be multiplied with each other.\n");
   else
   {
      printf("Enter the elements of second matrix\n");
 
      for ( c = 0 ; c < p ; c++ )
         for ( d = 0 ; d < q ; d++ )
            scanf("%d", &second[c][d]);
 
      for ( c = 0 ; c < m ; c++ )
      {
         for ( d = 0 ; d < q ; d++ )
         {
            for ( k = 0 ; k < p ; k++ )
            {
               sum = sum + first[c][k]*second[k][d];
            }
 
            multiply[c][d] = sum;
            sum = 0;
         }
      }
 
      printf("Product of entered matrices:-\n");
 
      for ( c = 0 ; c < m ; c++ )
      {
         for ( d = 0 ; d < q ; d++ )
            printf("%d\t", multiply[c][d]);
 
         printf("\n");
      }
   }
 
   return 0;
}