/in/foo.cc: In function 'int main()':
/in/foo.cc:36:10: warning: unused variable 'n1' [-Wunused-variable]
  int num,n1,n2,L,k,n;
          ^~
/in/foo.cc:61:11: warning: 'num' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<num;
           ^