/in/foo.cc: In function 'int main()':
/in/foo.cc:16:7: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
     if(i>0)
       ^
/in/foo.cc:20:7: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
     if(i<yushu)
       ^