/in/foo.cc: In function 'int main()':
/in/foo.cc:15:12: warning: statement has no effect [-Wunused-value]
     for (k1; k1<k2; k1++)
            ^
/in/foo.cc:17:9: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
      sum+=k1;
      ~~~^~~~