View Compilation Error

0_0_36432513_29072.cpp:20:1: error: 'unordered_map' does not name a type
 unordered_map<long long,long long>hs; 
 ^
0_0_36432513_29072.cpp: In function 'long long int BSGS(long long int, long long int, long long int)':
0_0_36432513_29072.cpp:27:2: error: 'hs' was not declared in this scope
  hs.clear();
  ^