foo.cc: In function ‘bool leap(int)’:
foo.cc:6:22: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
    6 |         return x%4==0&&x%100!=0||x%400==0;
      |                ~~~~~~^~~~~~~~~~
foo.cc: In function ‘int main()’:
foo.cc:31:21: warning: ‘a’ may be used uninitialized [-Wmaybe-uninitialized]
   31 |                 int a;
      |                     ^