#include <bits/stdc++.h>

using namespace std;
 
typedef long long ll;
typedef long double ld;
 
typedef pair<ll, ll> p;
 
#define MOD 1000000007

map<ll, ll> m;
map<ll, bool> c;

ll memo(ll x, ll y) {
	if(c[y]) return m[y];
	ll a;
	if(y == 1LL) {
		a = x - 1LL;
	} else if(y % 2LL) {
		a = min(abs(x - y), min(memo(x, (y + 1LL) / 2LL) + 2LL, memo(x, (y - 1LL) / 2LL) + 2LL));
	} else {
		a = min(abs(x - y), memo(x, y / 2LL) + 1LL);
	}
	c[y] = true;
	return m[y] = a;
}

int main() {
	cin.tie(0);
    ios::sync_with_stdio(false);

	ll X, Y;
	cin >> X >> Y;

	cout << memo(X, Y) << endl;
}
#include <algorithm>
#include <array>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
using namespace std;
typedef long long ll;
#define REP(i,n) for(ll i = 0; i < (ll)(n); ++i)
#define FOR(i,a,b) for(ll i = (a); i < (ll)(b); ++i)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(v) ((int)v.size())
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b; return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b; return true;
    }
    return false;
}
template<int MOD> struct Fp {
    ll val;
    constexpr Fp(ll v = 0) noexcept : val(v % MOD) {
        if (val < 0) val += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator - () const noexcept {
        return val ? MOD - val : 0;
    }
    constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator += (const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator -= (const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator *= (const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator /= (const Fp& r) noexcept {
        ll a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            ll t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator == (const Fp& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator != (const Fp& r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
        return os << x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, ll n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};
constexpr ll MOD = 1e9 + 7;
using mint = Fp<MOD>;

#define pb push_back
#define mp make_pair
#define mt make_tuple

int N, M;
vector<int> As;
vector<int> Xs;
vector<int> Ys;
vector<vector<int>> from_to;
vector<vector<int>> to_from;

vector<int> cache;
int dfs(int n) {
    if (cache[n] != -1e9) return cache[n];

    int mx = 0;
    for(auto v: from_to[n]) {
        chmax(mx, As[v]);
        chmax(mx, dfs(v));
    }
   return cache[n] = mx;
}

int main(void)
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    cin >> N >> M;
    As.resize(N);
    Xs.resize(M);
    Ys.resize(M);
    from_to.resize(N);
    cache.resize(N, -1e9);

    REP(n, N) cin >> As[n];
    REP(m, M) {
        int x, y;
        cin >> x >> y;
        --x; --y;
        from_to[x].pb(y);
    }
    cin >> N;

    int ans = -1e9;
    REP(n, N) {
        // 買うことができない
        if (SIZE(from_to[n]) == 0) continue;

        int tmp = dfs(n) - As[n];
        chmax(ans, tmp);
    }

    cout << ans << endl;


    return 0;
}
