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I am getting WA pls help me

#include<bits/stdc++.h>
using namespace std;
long long arr[20006],l[20007],r[20006],m[20007];
int main()
{
//freopen("out.txt","w",stdout);
long long i,j,n,key,cs,k;
cin>>cs;
for(k=1;k<=cs;k++){
cin>>n;
for(j=0;j<n-1;j++)
cin>>arr[j];
//cout<<n<<" input ...