#include <bits/stdc++.h>
using namespace std;
int SET(int n, int pos) { return n = n | (1 << pos); }
int RESET(int n, int pos) { return n = n & ~(1 << pos); }
int CHECK(int n, int pos) { return (bool)(n & (1 << pos)); }
int str2int(string s) {
  stringstream ss(s);
  int x;
  ss >> x;
  return x;
}
string int2str(int a) {
  stringstream ss;
  ss << a;
  string str = ss.str();
  return str;
}
string char2str(char a) {
  stringstream ss;
  ss << a;
  string str = ss.str();
  return str;
}
long long int bigMod(long long int n, long long int power, long long int MOD) {
  if (power == 0) return 1;
  if (power % 2 == 0) {
    long long int ret = bigMod(n, power / 2, MOD);
    return ((ret % MOD) * (ret % MOD)) % MOD;
  } else
    return ((n % MOD) * (bigMod(n, power - 1, MOD) % MOD)) % MOD;
}
long long int modInverse(long long int n, long long int MOD) {
  return bigMod(n, MOD - 2, MOD);
}
int POW(int x, int y) {
  int res = 1;
  for (; y;) {
    if ((y & 1)) {
      res *= x;
    }
    x *= x;
    y >>= 1;
  }
  return res;
}
int inverse(int x) {
  double p = ((double)1.0) / x;
  return (p) + 1e-9;
}
int gcd(int a, int b) {
  while (b) b ^= a ^= b ^= a %= b;
  return a;
}
int nC2(int n) { return n * (n - 1) / 2; }
long long int MOD(long long int n, long long int mod) {
  if (n >= 0)
    return n % mod;
  else if (-n == mod)
    return 0;
  else
    return mod + (n % mod);
}
int n, m, k, data[1000005];
int main() {
  scanf("%d %d %d", &n, &m, &k);
  for (int i = 0; i < m; i++) {
    int p;
    scanf("%d", &p);
    data[p] = 1;
  }
  int bone = 1;
  bool ff = 0;
  if (data[1]) ff = 1;
  for (int i = 0; i < k; i++) {
    int a, b;
    scanf("%d %d", &a, &b);
    if (ff) continue;
    if (a == bone) {
      bone = b;
      if (data[b]) ff = 1;
    } else if (b == bone) {
      bone = a;
      if (data[a]) ff = 1;
    }
  }
  printf("%d\n", bone);
  return 0;
}
