View Compilation Error

0_0_38950465_3372.cpp: In function 'int main()':
0_0_38950465_3372.cpp:21:31: error: expected unqualified-id before '::' token
   21 |                 for(set<int>::::iterator i=sum.begin();i!=sum.end();i++){
      |                               ^~
0_0_38950465_3372.cpp:21:56: error: 'i' was not declared in this scope
   21 |                 for(set<int>::::iterator i=sum.begin();i!=sum.end();i++){
      |                                                        ^