Tree Houses Long Challenge (Help needed pls)

[kdraconis777]

I tried following the editorial to come up with a solution to the Tree House problem in the May Long Challenge 2021. Can anyone help me figure out how I can further refine my code to pass the last two cases. The problem and solution I came up with is given below:

Problem:

THOUSES Problem - CodeChef

Solution:
https://www.codechef.com/viewsolution/46672786

[suman_18733097]

ACfied

#include<bits/stdc++.h>
#define MOD 1000000007
using namespace std;
typedef unsigned long long ull;
ull solve(ull v, ull parent, vector<vector<ull>>& tree)
{
    vector<ull> vals;
    for (ull u: tree[v])
        if (u != parent)
            vals.push_back(solve(u, v, tree));

    sort(vals.rbegin(), vals.rend());

    ull ret = 1;
    ull mult = 1;
    for (ull u: vals)
        ret += (mult++)*u;

    return ret;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    ull t; cin>>t;

    while (t--)
    {
        ull n, x; cin>>n>>x;
        vector<vector<ull>> tree(n);
        for (ull i = 0; i < n - 1; ++i)
        {
            ull u, v;
            cin>>u>>v;
            tree[u - 1].push_back(v - 1);
            tree[v - 1].push_back(u - 1);
        }
        
        cout<<(solve(0, -1, tree) % MOD * x % MOD)%MOD<<"\n";
    }

    return 0;
}

Can you find the mistake yourself?

[kdraconis777]

Oh so basically, the final product could overflow. Thanks a lot, man.

[beware_of_me_d]

how do u put the code like?

[suman_18733097]