#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e5 + 5;
int N, M, deg[maxn], w[maxn];

int main() {
  //  freopen("a.in", "r", stdin);
  //  freopen("a.out", "w", stdout);
  scanf("%d%d", &N, &M);
  for (int i = 1; i <= N; i++) scanf("%d", &w[i]);
  vector<multiset<int> > st(N + 1);
  for (int i = 1; i <= M; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    deg[u]++;
    deg[v]++;
  }
  if (N == 1) {
    printf("%d\n", w[1]);
    return 0;
  }
  int ans = 0;
  for (int i = 1; i <= N; i++) {
    if (deg[i] >= 2) {
      ans = max(ans, w[i]);
    }
  }
  printf("%d\n", ans);
  return 0;
}