#include <bits/stdc++.h>


using namespace std;

using lll = __int128_t;
using ll = long long;
using ld = long double;

#define len(a) ((int)(a).size())
#define rep(i, n) for(int i = 0; i < (n); i += 1)


mt19937 rnd(234);


int n;
ll a, b, p;
vector<int> perm;
ll inva, invb;



ll bin_pow(ll x, ll n) {
    ll rs = 1;
    for (ll i = 1; i <= n; i *= 2, x = lll(x) * x % p)
        if (n & i) rs = lll(rs) * x % p;
    return rs;
}

ll inv(ll x) {
    return bin_pow(x, p - 2);
}


ll forward(ll x) {
    return (lll(x) * a + b) % p;
}


ll backward(ll x) {
    return (lll(x + invb) * inva) % p;
}


int32_t main() {
    if (1) {
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout.tie(0);
    }
    cin >> n;
    perm.resize(n + 1);
    for (int i = 1; i <= n; i += 1) {
        cin >> perm[i];
    }
    cin >> a >> b >> p;
    inva = inv(a);
    invb = (p - b) % p;
    ll t = -1;
    for (int i = 1; i <= n; i += 1) {
        if (perm[i] == n) {
            t = i - 1;
            swap(perm[i], perm[n]);
            break;
        }
    }
    ll s = -1;
    for (int i = 1; i <= n - 1; i += 1) {
        if (perm[i] == n - 1) {
            s = i - 1;
            swap(perm[i], perm[n - 1]);
            break;
        }
    }
    assert(t != -1 and s != -1);
    ll f = 1e6;
    vector<vector<ll>> mp(n);
    rep(h, f) {
        ll val = (lll(a) * s + b) % p;
        val = (val + lll(h) * a % p * f % p * (n - 1)) % p;
        mp[val % n].push_back(h);
    }
    auto check = [&](ll x) -> ll {
        if (x % (n - 1) != s) return -1;
        if (forward(x) % n != t) return -1;
        vector<pair<int, int>> swaps;
        x = backward(x);
        bool ok = true;
        for (int i = n - 2; i >= 1; i -= 1) {
            int t = x % i + 1;
            if (perm[t] != i) {
                ok = false;
                break;
            }
            swap(perm[t], perm[i]);
            swaps.push_back(make_pair(t, i));
            x = backward(x);
        }
        reverse(swaps.begin(), swaps.end());
        for (auto [i, j] : swaps) swap(perm[i], perm[j]);
        if (!ok) {
            return -1;
        }
        return x;
        };
    rep(l, f) {
        ll val = lll(l) * a % p * (n - 1) % p;
        val %= n;
        ll first = (t + n - val) % n;
        ll second = (t + n - (val + p) % n) % n;
        for (auto z : { first, second }) {
            for (auto h : mp[z]) {
                ll x = (s + lll(l + f * h) * (n - 1)) % p;
                if (check(x)) {
                    cout << x << "\n";
                    return 0;
                }
            }
        }
    }
    assert(0);
    return 0;
}