I am explaining how G function is working.

Number Binary repr. xor from 1 to n A(1)^A(2)...^A(n)

• 0 0000 0000 0000=0
• 1 0001 0001 0001=1
• 2 0010 0011 0010=2
• 3 0011 0000 0010=2
• 4 0100 0100 0110=6
• 5 0101 0001 0111=7
• 6 0110 0111 0000=0
• 7 0111 0000 0000=0

from above we can deduce that G is periodic function with period of 8 now for a==0 or a==1 value is x for a==2 or a==3 value is 2 for a==4 or a==5 value is x+2 for a==6 or a==7 value is 0 For better undestanding how to calculate xor of 1 to n efficiently please refer this link:-xor from 1 to n here is my solution

#include<bits/stdc++.h>
using namespace std;
long long uptonxor(long long n)
{
    int a=n%8;
    if(a==0 || a==1)
        return n;
    else if(a==2 || a==3)
        return 2;
    else if(a==4 || a==5)
        return n+2;
    return 0;
}
int main()
{
    int q;
    cin>>q;
    while(q--)
    {
        long long l,r;
        cin>>l>>r;
        long long ans;
        ans=uptonxor(l-1)^uptonxor(r);
        cout<<ans<<endl;
    }
    return 0;
}