foo.cc: In function ‘int main()’:
foo.cc:8:18: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
    8 |         if(y%4==0&&y%100!=0||y%400==0) mday[2]=29;
      |            ~~~~~~^~~~~~~~~~
foo.cc:6:23: warning: unused variable ‘d2’ [-Wunused-variable]
    6 |         int y,m,d,h,k,d2,leap=0;
      |                       ^~
foo.cc:6:26: warning: unused variable ‘leap’ [-Wunused-variable]
    6 |         int y,m,d,h,k,d2,leap=0;
      |                          ^~~~