foo.cpp: In function 'double weight()':
foo.cpp:34:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k;
          ^
foo.cpp: In function 'void build(int, int, int&)':
foo.cpp:66:6: warning: unused variable 'i' [-Wunused-variable]
  int i,j,k,mid=(l+r)>>1;
      ^
foo.cpp:66:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j,k,mid=(l+r)>>1;
        ^
foo.cpp:66:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k,mid=(l+r)>>1;
          ^
foo.cpp: In function 'void Spilt(int, int, int&, int&)':
foo.cpp:78:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k;
          ^
foo.cpp: In function 'int Merge(int, int)':
foo.cpp:96:6: warning: unused variable 'k' [-Wunused-variable]
  int k;
      ^
foo.cpp: In function 'void init()':
foo.cpp:117:24: error: 'b' was not declared in this scope
  rep(i,1,n)a[i]=read(),b[i]=++tot;
                        ^
foo.cpp:115:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j,k;
        ^
foo.cpp:115:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k;
          ^
foo.cpp: In function 'void work()':
foo.cpp:122:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j,k,p,t,c;
        ^
foo.cpp:122:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k,p,t,c;
          ^