C++ :

#include<bits/stdc++.h>
using namespace std;
int N,t=1;
int main()
{
    cin>>N;
    for(int j=1;j<=N;j++)
    {
    	if(j%2==1){
    		for(int i=t;i<t+N;i++) cout<<i<<" ";
    		t+=N;
    		cout<<endl;
    	}
    	else{
    		for(int i=t+N-1;i>=t;i--) cout<<i<<" ";
    		t+=N;
    		cout<<endl;
    	}
    }
}