foo.cc: In function ‘bool leap1(int)’:
foo.cc:7:23: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
    7 |         return(y1%4==0&&y1%100!=0||y1%400==0);
      |                       ^
foo.cc: In function ‘bool leap2(int)’:
foo.cc:11:23: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
   11 |         return(y2%4==0&&y2%100!=0||y2%400==0);
      |                ~~~~~~~^~~~~~~~~~~