/in/foo.cc: In function 'int rn(int)':
/in/foo.cc:12:17: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   12 |  if (y % 4 == 0 && y % 100 != 0 || y % 400 == 0) return 1;
      |      ~~~~~~~~~~~^~~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:28:14: warning: statement has no effect [-Wunused-value]
   28 |   else mo[2] == 28;
      |        ~~~~~~^~~~~
/in/foo.cc:36:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   36 |    while (sum >= 365 && rn(yr + 1) == 0 || sum >= 366 && rn(yr + 1) == 1) {
      |           ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~