#include <stdio.h>

        static const double grid[4][2] = {
         {-3/3.,-1/3.},{+1/3.,-3/3.},
         {-1/3.,+3/3.},{+3/3.,+1/3.}
        };

        int main() {
          for (int i = 0; i < 4; i++)
            printf("%d:%.2f,%.2f ", i, grid[i][0], grid[i][1]);
          printf("\n");
          return 0;
        }