/in/foo.c: In function 'runnian':
/in/foo.c:7:12: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  if (y%4==0&&y%100!=0||y%400==0)
      ~~~~~~^~~~~~~~~~
/in/foo.c: In function 'main':
/in/foo.c:16:14: warning: unused variable 'days' [-Wunused-variable]
  int i,y,m,d,days=-1;
              ^~~~