stl - Does set<pair<long long,long long> > does not supports members first an second? -

 #include <bits/stdc++.h>  using namespace std;  #define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0); #define ll long long int #define pb push_back #define mp make_pair #define pii pair<int,int> #define pll pair<ll,ll> #define pis pair< int,string>   #define test int t;cin>>t;while(t--) #define ff first // error: 'std::set<std::pair<long long int, long long int> >::iterator' has no member named 'first' #define ss second // error: 'std::set<std::pair<long long int, long long int> >::iterator' has no member named 'second' #define inf 1000000000 #define input(a,n) for(i=1;i<=n;i++)cin>>a[i]; #define output(a,n) for(i=1;i<=n;i++)cout<<a[i]<<" "; vector< vector<ll> > v(3002, vector<ll>(3002,-1)); set< pair<ll, ll> > se; set< pair<ll, ll> >::iterator it; int vis[3002]={0}; void exmin(ll a) {     ll x,des,val,min=inf;     for(x=0;x<v[a].size();x++)     {         if(v[a][x]<min)         {             val=v[a][x];             des=x;             min=val;         }     }     se.insert(mp(val,des)); }   int main() {    fast   ll n,m,x,i,j,k,wt=0,s;   cin>>n>>m;   vector<int> ve;   for(x=1;x<=n;x++)      ve.pb(x);   for(x=0;x<m;x++)   {     cin>>i>>j>>k;     if(v[i][j]!=-1)     {         if(v[i][j]>k)         {             v[i][j]=k;             v[j][i]=k;           }       }       else       {         v[i][j]=k;         v[j][i]=k;       }    }   cin>>s;   ve.erase(ve.begin()+s-1);   while(ve.size()!=0)   {     for(x=0;x<v[s].size();x++)     {         if(v[s][x]!=-1 && vis[x]!=1)         {             exmin(x);           }     } /*  for(x=0;x<p.size();x++)     {      }*/      it=se.begin();     wt=wt+*(it).ff;     s=*(it).ss;     vis[*(it).ss]=1;     ve.erase(ve.begin()+*(it).ss-1);      se.erase(it);   }  return 0; } 

still facing errors.
trying implement prim's algorithm.
not able include line numbers, hence attached errors along lines itself.
sorry , not including "abhorrent part" because error in part.

although have global set s

set< pair<ll, ll> > s; 

you have defined local variable s of type long long:

ll n,m,x,i,j,k,wt=0,s; 

which hides global s. long long has neither begin nor erase member functions since primitive type. hence errors:

 it=s.begin();    //error: request member 'begin' in 's', of non-class type 'long long int'   s.erase(it);  //error: request member 'erase' in 's', of non-class type 'long long int' 

to refer global s, use ::s, i.e.

::s.erase(it); 

and lastly want point out "contestese" coding style you're using abhorrent. feel free use during contests as like, please edit away when post questions on so.