#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;
typedef long long ll;
typedef pair<ll,ll> P;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define EFOR(i,a,b) for(int i=(a);i<=(b);++i)
#define REP(i, n) FOR(i,0,n)
#define INF 1e12

int main(void){
    ll n,m, ans_max = -INF;
    cin >> n >> m;
    vector<ll> a(n, 0);
    vector<P> root(m);
    vector<ll> ans(n, INF);

    REP(i, n) cin >> a[i];

    REP(i, m) cin >> root[i].first >> root[i].second;

    sort(root.begin(), root.end());

    REP(i, m){
        ll from = root[i].first, to = root[i].second;
        from--; to--;
        ans[to] = min({ans[to], ans[from], a[from]});
    }

    REP(i, n){
        ans_max = max(ans_max, a[i] - ans[i]);
    }
    cout << ans_max << endl;

    return 0;
}
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
// --------------------------------------------------------
template<class T> bool chmax(T& a, const T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T& a, const T b) { if (b < a) { a = b; return 1; } return 0; }
#define FOR(i,l,r) for (ll i = (l); i < (r); ++i)
#define RFOR(i,l,r) for (ll i = (r)-1; (l) <= i; --i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define SORT(c) sort(ALL(c))
#define RSORT(c) sort(RALL(c))
#define MIN(c) *min_element(ALL(c))
#define MAX(c) *max_element(ALL(c))
#define SUMLL(c) accumulate(ALL(c), 0LL)
#define COUNT(c,v) count(ALL(c),(v))
#define SZ(c) ((ll)(c).size())
#define BIT(b,i) (((b)>>(i)) & 1)
#define PCNT(b) __builtin_popcountll(b)
#define CIN(c) cin >> (c)
#define COUT(c) cout << (c) << '\n'
#define debug(x) cerr << "l." << __LINE__ << " : " << #x << " = " << (x) << '\n'
ll llceil(ll a, ll b) { return (a + b - 1) / b; }
ll bitlen(ll b) { if (b <= 0) { return 0; } return (64LL - __builtin_clzll(b)); }
string toupper(const string& S) { string T(S); REP(i,SZ(T)) T[i] = toupper(T[i]); return T; }
string tolower(const string& S) { string T(S); REP(i,SZ(T)) T[i] = tolower(T[i]); return T; }
template<class T> void cout_line(const vector<T>& ans, ll l, ll r) { for (ll i = l; i < r; i++) { if (i != l) { cout << " "; } cout << ans[i]; } cout << '\n'; }
template<class T> void debug_line(const vector<T>& ans, ll l, ll r, ll L = 0) { cerr << "l." << L << " :"; for (ll i = l; i < r; i++) { cerr << " " << ans[i]; } cerr << '\n'; }
using P = pair<ll,ll>;
using VP = vector<P>;
using VVP = vector<VP>;
using VS = vector<string>;
using VVS = vector<VS>;
using VLL = vector<ll>;
using VVLL = vector<VLL>;
using VVVLL = vector<VVLL>;
using VB = vector<bool>;
using VVB = vector<VB>;
using VVVB = vector<VVB>;
using VD = vector<double>;
using VVD = vector<VD>;
using VVVD = vector<VVD>;
using VLD = vector<ld>;
using VVLD = vector<VLD>;
using VVVLD = vector<VVLD>;
static const double EPS = 1e-10;
static const double PI  = acos(-1.0);
static const ll MOD = 1000000007;
// static const ll MOD = 998244353;
static const ll INF = (1LL << 62) - 1;  // 4611686018427387904 - 1
// --------------------------------------------------------
// #include <atcoder/all>
// using namespace atcoder;

ll pow_mod(ll x, ll n, ll mod) {
    ll res = 1;
    if (n > 0) {
        res = pow_mod(x, n / 2, mod);
        if (n % 2 == 0) res = (res * res) % mod;
        else res = (((res * res) % mod) * x) % mod;
    }
    return res;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);

    ll N, M; cin >> N >> M;

    ll ans = (pow_mod(10,N,M*M) - pow_mod(10,N,M)) / M;
    COUT(ans);

    return 0;
}
