foo.cc: In function 'void click(int, int)':
foo.cc:20:35: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
  if (k - 1 >= 0) a[row] ^= 1 << k - 1;
                                 ~~^~~
foo.cc:21:35: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
  if (k + 1 <= 4) a[row] ^= 1 << k + 1;
                                 ~~^~~
foo.cc: In function 'int main()':
foo.cc:47:17: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
     temp = temp - temp & -temp;
            ~~~~~^~~~~~
foo.cc:57:18: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses]
      temp = temp - temp & -temp;
             ~~~~~^~~~~~