unghidrept

/// C++ program to count number of edge in undirected graph
#include<bits/stdc++.h>
using namespace std;

class Graph /// Adjacency list representation of graph
{
    int V ;
    list <int> *adj;
public :
    Graph(int V)
    {
        this->V=V ;
        adj=new list<int>[V];
    }
    void addEdge( int u,int v);
    int countEdges() ;
};

void Graph::addEdge(int u,int v) /// add edge to graph
{
    adj[u].push_back(v);
    adj[v].push_back(u);
}

/// Returns count of edge in undirected graph
int Graph::countEdges()
{
    int sum=0;
    /// traverse all vertex
    for(int i=0;i<V;++i)
        sum+=adj[i].size(); /// add all edge that are linked to the current vertex
    /// The count of edge is always even because in undirected graph every edge is connected twice between two vertices
    return sum/2;
}

int main()
{
    int n,x,y,V=200001;
    Graph g(V); /// making above uhown graph
    cin>>n;
    for(int i=1;i<=n;++i)
        cin>>x>>y,g.addEdge(x,y);
    cout<<g.countEdges()/2<<'\n';
    return 0;
}