View Compilation Error

0_0_37822077_9109.cpp:22:1: error: 'set' does not name a type
 set<pair<ll, int>> ans;
 ^
0_0_37822077_9109.cpp: In function 'void dijkstra()':
0_0_37822077_9109.cpp:27:3: error: 'ans' was not declared in this scope
   ans.insert({ dis[i],i });
   ^
0_0_37822077_9109.cpp:28:10: error: 'ans' was not declared in this scope
  while (!ans.empty()) {
          ^