/in/foo.cc: In function 'int gcd(int, int)':
/in/foo.cc:10:9: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return r;
         ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:15:16: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
   cout<<gcd(a,b)<<endl;
                ^