RT，三个RE和一个AC

#include<iostream>
#include<cmath>
#include<iomanip>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
long long int n,q,ans;
long long int s;
vector<vector<long long int> > a(n+5);
int main(){
    scanf("%lld%lld",&n,&q);
    for(int i=0;i<n;i++){
        scanf("%lld",&s);
        if(a[i].size()<s){
            a[i].resize(s+5);
        }
        for(int j=0;j<s;j++){
            scanf("%lld",&a[i][j]);
        }
    }
    for(int i=0;i<q;i++){
        long long int x,y;
        scanf("%lld%lld",&x,&y);
        x--;
        y--;
        if(i==0){
            ans=a[x][y];
        }else
            ans=ans^a[x][y];
    }
    printf("%lld",ans);
    return 0;
}