/in/foo.cc:8:7: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main ()
       ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:15:6: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
    if(x1==x2)
      ^
/in/foo.cc:19:7: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
    if (y1==y2)
       ^