#include <stdio.h>
#include <stdlib.h>
#define L (32768-1)
#define XAXIS 20
#define YAXIS 20

void make_lattice(int lattice[][YAXIS])
{
  int m, n;
  for(m = 0; m < XAXIS; ++m){
    for(n = 0; n < YAXIS; ++n){
      if((double)rand()/L>0.5) lattice[m][n] = 1;
      else lattice[m][n] = -1;
    }
  }
}

void display(int lattice[][YAXIS])
{
  int m, n;
  for(m = 0; m < XAXIS; ++m){
    for(n = 0; n < YAXIS; ++n){
      if(lattice[m][n] == 1) printf("○");
      else printf("●");
    }
    printf("\n");
  }
}

main()
{
  int lattice[XAXIS][YAXIS];

  srand(5);

  make_lattice(lattice);
  display(lattice);
}