Tree input Generator

/***** TheAnshul *****/

#include<bits/stdc++.h>
#define ll          long long
#define pb          push_back
#define ppb         pop_back
#define endl        '\n'
#define mii         map<ll int,ll int>
#define msi         map<string,ll int>
#define mis         map<ll int, string>
#define rep(i,a,b)    for(ll int i=a;i<b;i++)
#define mpi         map<pair<ll int,ll int>,ll int>
#define pii         pair<ll int,ll int>
#define vi          vector<ll int>
#define vii         vector<pair<ll int, ll int>>
#define vs          vector<string>
#define all(a)      (a).begin(),(a).end()
#define F           first
#define S           second
#define sz(x)       (ll int)x.size()
#define hell        1000000007
#define lbnd        lower_bound
#define ubnd        upper_bound
#define bs          binary_search
#define mp          make_pair
#define what_is(x)  cerr << #x << " is " << x << endl;
using namespace std;
#define N  200000          // to generate n change vale of N here.
ll n=N;
// ll n=rand()%(N-1)+1;
bool vis[N+5];
ll last=2;
vi a[N+5];
void dfs(ll node)
{
    vis[node]=1;
    int ch=rand()%10+1;
    rep(i,0,ch)
    {
        a[node].pb(last);
        a[last].pb(node);
        cout<<last<<" "<<node<<endl;
        last++;
        if(last==n+1)
            exit(0);
    }
    for(auto i:a[node])
    if(!vis[i])
    dfs(i);
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int TESTS=1;
//  cin>>TESTS;
            /************************************/
            // freopen("input.txt","r",stdin);
            freopen("input.txt","w",stdout);
            /***********************************/
    while(TESTS--)
    {
        cout<<n<<endl;
        dfs(1);
    }
    return 0;
}