View Compilation Error

0_0_30431470_2959.cpp:6:1: error: 'unordered_map' does not name a type
 unordered_map<bitset<maxn>,int>mp;
 ^
0_0_30431470_2959.cpp: In function 'int main()':
0_0_30431470_2959.cpp:11:9: error: 'mp' was not declared in this scope
         mp.clear();
         ^