Chef and Queries

#include<bits/stdc++.h>
using namespace std;

const long long mod = 1LL << 32;
const long long M = (1LL << 31);

bitset<M> b;

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    int q;
    long long S, A, B;
    cin >> q >> S >> A >> B;
    long long ans = 0;
    for (int i = 1; i <= q; i++)
    {
        long long val = (S >> 1);
        if (S & 1)
        {
            if (b[val] == 0)
            {
                ans += val;
            }
            b[val] = 1;
        }
        else
        {
            if (b[val] == 1)
            {
                ans -= val;
            }
            b[val] = 0;
        }
        S = (A * S + B) % mod;
    }
    cout << ans << "\n";
    return 0;
}