void killOthers(int row, int col, int x)
{
  for(int i=0;i<9;i++)
  {
    myBox[row][i].ruleOut(x); 
    myBox[i][col].ruleOut(x);
  }
  
  
    int iBase = row - row%3;
    int jBase = col - col%3;
    for(int i=0;i<3;i++)
      for(int j=0;j<3;j++)
         myBox[iBase+i][jBase + j].ruleOut(x);
  
}