View Compilation Error

0_0_36777970_4021.cpp:30:1: error: 'unordered_map' does not name a type
 unordered_map<int, int> mp;
 ^
0_0_36777970_4021.cpp: In function 'double Closest_Pair(int, int)':
0_0_36777970_4021.cpp:39:12: error: 'mp' was not declared in this scope
         if(mp[L] || mp[R]) return dis;
            ^
0_0_36777970_4021.cpp:60:13: error: 'mp' was not declared in this scope
         if(!mp[P[i].id] && fabs(P[i].x - P[mid].x) <= dis){
             ^
0_0_36777970_4021.cpp: In function 'int main()':
0_0_36777970_4021.cpp:95:9: error: 'mp' was not declared in this scope
         mp.clear();
         ^