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

#define MAX_SIZE 1000

void initArray ( char A[][MAX_SIZE], int r )
{
   int i, j;

   for (i=0; i<=2*r; ++i) {
      for (j=0; j<=2*r; ++j) A[i][j] = ' ';
      A[i][2*r] = '\0';
   }
}

void printArray ( char A[][MAX_SIZE], int r )
{
   int i, j;

   for (i=0; i<=2*r; ++i) {
      for (j=0; j<=2*r; ++j) printf(" %c", A[i][j]);
      printf("\n");
   }
}

void drawCircle ( char A[][MAX_SIZE], int r, int R )
{
   int x, y;

   for (x=0; x<=R; ++x) {
      y = round(sqrt(R*R - x*x));
      A[r+x][r+y] = '@';
      A[r+x][r-y] = '@';
      A[r-x][r+y] = '@';
      A[r-x][r-y] = '@';
      A[r+y][r+x] = '@';
      A[r+y][r-x] = '@';
      A[r-y][r+x] = '@';
      A[r-y][r-x] = '@';
   }
}

void refineCircle ( char A[][MAX_SIZE], int r )
{
   int x, y;

   for (x=1; x<2*r; ++x) {
      for (y=1; y<2*r; ++y) {
         if ((A[x][y] == ' ') && (A[x][y-1] != ' ') && (A[x][y+1] != ' ') && (A[x+1][y] != ' ') && (A[x-1][y] != ' ')) {
            A[x][y] = '@';
         }
      }
   }
}

int main ()
{
   int r, t, i;
   char A[MAX_SIZE][MAX_SIZE];

   printf("Enter radius (r): "); scanf("%d", &r);
   printf("Enter thickness (t): "); scanf("%d", &t);
   initArray(A,r);
   drawCircle(A,r,r);
   printf("\n+++ Circle of thickness 1:\n");
   printArray(A,r);
   for (i=1; i<t; ++i) drawCircle(A,r,r-i);
   printf("\n+++ Circle of thickness %d:\n", t);
   printArray(A,r);
   refineCircle(A,r);
   printf("\n+++ Circle of thickness %d after refinement:\n", t);
   printArray(A,r);
   exit(0);
}