/in/foo.cc: In function 'int main(int, char**)':
/in/foo.cc:11:12: warning: unused variable 'k' [-Wunused-variable]
  int i, j, k;
            ^
/in/foo.cc: In function 'int Mul(BigInt*, int)':
/in/foo.cc:68:14: warning: unused variable 'k' [-Wunused-variable]
  int jw = 0, k = 0;
              ^
/in/foo.cc: In function 'int main(int, char**)':
/in/foo.cc:19:10: warning: 'nb' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int na, nb;
          ^~
/in/foo.cc:19:6: warning: 'na' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int na, nb;
      ^~