diagonal 2d number sequences

#include <stdio.h>


main()
{
      int x[100][100],a,i,j;
      scanf("%d",&a);
      for( i = 0 ; i < a ; i++ )
           for( j = 0 ; j < a ; j++ )
                scanf("%d",&x[i][j]);
      for( i = 0 ; i < a ; i++ )
           for( j = 0 ; j <= i ; j++ )
                printf("%d ",x[i-j][j]);
      for( i = a ; i < 2 * a - 1 ; i++ )
           for( j = a - 1 ; j >= i - (a-1) ; j-- )
                printf("%d ",x[j][i-j]);
}