View Compilation Error

0_0_37640084_19854.cpp:14:1: error: 'unordered_map' does not name a type
 unordered_map<int,int>change;
 ^
0_0_37640084_19854.cpp: In function 'int main()':
0_0_37640084_19854.cpp:77:13: error: 'change' was not declared in this scope
             change[alls[i]]=find(alls[i]);
             ^
0_0_37640084_19854.cpp:82:19: error: 'change' was not declared in this scope
             int l=change[a[i].first],r=change[a[i].second];
                   ^
0_0_37640084_19854.cpp:84:20: error: 'r' was not declared in this scope
             update(r+1,-1);
                    ^
0_0_37640084_19854.cpp:96:9: error: 'change' was not declared in this scope
         change.clear();
         ^