#include<iostream>
#include<cstdio>
using namespace std;
inline int read(){
    int num=0,t=1;char c=getchar();
    while(c>‘9‘||c<‘0‘){if(c==‘-‘)t=-1;c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){num=num*10+c-‘0‘;c=getchar();}
    return num*t;
}
struct Yzy{int qian,hou;}q[500010];
int n,m;
int main()
{
    n=read();
    for(int i=1;i<=n;i++){
        q[i].qian=i-1;q[i].hou=i+1;
        if(i==1){q[i].qian=-1;}
        if(i==n){q[i].hou=-1;}
    }
    for(int i=1;i<=n;i++){
        m=read();
        printf("%d %d\n",q[m].qian,q[m].hou);
        q[q[m].qian].hou=q[m].hou;q[q[m].hou].qian=q[m].qian;
    }
    return 0;
}

#include<iostream>
#include<cstdio>
using namespace std;
int read(){
    int t=1,num=0;char c=getchar();
    while(c>‘9‘||c<‘0‘){if(c==‘-‘)t=-1;c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){num=num*10+c-‘0‘;c=getchar();}
    return num*t;
}
const int mn=5e5;
struct hehe{int t,nxt,w;}e[mn*2+5];
int num=0,h[mn+5],size[mn+5],ans=0,n;
void add(int f,int t,int w){e[++num]=(hehe){t,h[f],w};h[f]=num;}
void dfs(int x,int fa){
    size[x]=1;
    for(int i=h[x];i;i=e[i].nxt){
        if(e[i].t!=fa){
            dfs(e[i].t,x);size[x]+=size[e[i].t];
            if(size[e[i].t]&1)ans^=e[i].w;
        }
    }
}
int main()
{
    n=read();if(n&1){puts("0");return 0;}
    for(int i=1;i<n;i++){
        int x,y,z;
        x=read();y=read();z=read();
        add(x,y,z);add(y,x,z);
    }
    dfs(1,0);printf("%d\n",ans);
    return 0;
}

#include<iostream>
#include<cstdio>
using namespace std;
inline int read(){
    int num=0,t=1;char c=getchar();
    while(c>‘9‘||c<‘0‘){if(c==‘-‘)t=-1;c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){num=num*10+c-‘0‘;c=getchar();}
    return num*t;
}
int a[2010][2010]={0},n;
int main()
{
    n=read();
    if(n>500){puts("0");return 0;}
    for(int i=1;i<n;i++){
        int u,v,w;
        u=read();v=read();w=read();
        a[v][u]=a[u][v]=w;
    }
    for(int k=1;k<=n;k++){
        for(int i=1;i<=n;i++){
            for(int j=1;j<=n;j++){
                if(a[i][k]&&a[k][j]&&(!a[i][j])){
                    a[i][j]=(a[i][k]^a[k][j]);
                }
            }
        }
    }
    int ans=0;
    for(int i=1;i<n;i++){
        for(int j=i+1;j<=n;j++){
            if(i==j)continue;
            ans=(ans^a[i][j]);
        }
    }
    printf("%d\n",ans);
    return 0;
}