View Compilation Error

0_0_28671406_10720.cpp: In function 'int main()':
0_0_28671406_10720.cpp:54:17: error: 'sort' was not declared in this scope
   sort(b+1,b+1+n);
                 ^
0_0_28671406_10720.cpp:55:27: error: 'unique' was not declared in this scope
   int len=unique(b+1,b+1+n)-b-1;
                           ^