MULTHREE problem, can anyone tell me what's wrong?

#include “bits/stdc++.h”
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define boost() ios::sync_with_stdio(0); cin.tie(0), cout.tie(0);

void solve()
{
ull k;
ull d0, d1, d2;
cin >> k >> d0 >> d1;

d2 = d0 + d1;
ll x = (k-3) / 4;
ll rem = (k-3) % 4;
ll sum = 0;
sum += d0 + d1 + d2;

ll d3 = (2 * d2) % 10;
ll d4 = (4 * d2) % 10;
ll d5 = (8 * d2) % 10;
ll d6 = (6 * d2) % 10;

ll xsum = d3 + d4 + d5 + d6;
ll t = xsum * x;
sum += t;

if(rem == 1) { sum += d3; }
else if(rem == 2) { sum += (d3 + d4); }
else if(rem == 3) { sum += (d3 + d4 + d5); } 


if(sum % 3 == 0)
	cout << "YES\n";
else
	cout << "NO\n";

}

int main()
{
boost();

ll t = 1;
cin >> t;
while(t--) 
{
	solve();
}
return 0;

}

what if k == 2?
sum = d0 + d1 + d2 ?

d2 = ( d0 + d1 ) % 10

Fixed it, got accepted, thank you

Can someone tell me what I am doing wrong?

https://www.codechef.com/viewsolution/33143536