/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:8:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(i%400==0||i%4==0&&i%100!=0)
                ~~~~~~^~~~~~~~~~
/in/foo.c:5:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j;
        ^