#include <bits/stdc++.h>
inline int two(int n) { return 1 << n; }
inline int test(int n, int b) { return (n >> b) & 1; }
inline void set_bit(int& n, int b) { n |= two(b); }
inline void unset_bit(int& n, int b) { n &= ~two(b); }
inline int last_bit(int n) { return n & (-n); }
inline int ones(int n) {
  int res = 0;
  while (n && ++res) n -= n & (-n);
  return res;
}
long long int gcd(long long int a, long long int b) {
  return (a ? gcd(b % a, a) : b);
}
long long int modPow(long long int a, long long int b, long long int MOD) {
  long long int x = 1, y = a;
  while (b > 0) {
    if (b % 2 == 1) {
      x = (x * y) % MOD;
    }
    b /= 2;
    y = (y * y) % MOD;
  }
  return x;
}
long long int modInverse(long long int a, long long int p) {
  return modPow(a, p - 2, p);
}
using namespace std;
const int N = 2e5 + 5;
int arr[N];
int seq[N];
int n, k, a, m;
bool isPossible(int p) {
  int i, j;
  for (int i = 0; i < (n + 1); i++) seq[i] = 0;
  for (int i = 0; i < (p); i++) seq[arr[i]]++;
  for (int i = (1); i <= (n); i++) seq[i] += seq[i - 1];
  int idx = 0;
  int ctr = 0;
  while (idx + a <= n && ctr < k) {
    if (seq[idx] == seq[idx + a]) {
      ctr++;
      idx += a + 1;
    } else
      idx++;
  }
  return (ctr == k);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int hi, lo, mid, i, j, l, ans;
  cin >> n >> k >> a;
  cin >> m;
  for (int i = (0); i <= (m - 1); i++) cin >> arr[i];
  if (isPossible(m)) {
    cout << "-1\n";
    return 0;
  }
  lo = 0;
  hi = m + 2;
  while (lo <= hi) {
    mid = (lo + hi) / 2;
    if (isPossible(mid)) {
      ans = mid;
      lo = mid + 1;
    } else
      hi = mid - 1;
  }
  cout << ans + 1;
  return 0;
}
