/in/foo.c:2:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:11:10: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
 if(i%4==0&&i%100!=0||i%400==0)
    ~~~~~~^~~~~~~~~~