#include <bits/stdc++.h>
int dx[] = {0, 0, -1, 1, 1, -1, -1, 1};
int dy[] = {1, -1, 0, 0, 1, -1, 1, -1};
using namespace std;
void file() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
void solve(int x) { solve(1); }
int main() {
  file();
  int n, k, a;
  cin >> n >> k >> a;
  int m;
  cin >> m;
  set<int> end;
  map<int, int> start;
  start[n] = 1;
  end.insert(n);
  int cnt = (n + 1) / (a + 1);
  for (int i = 1; i <= m; i++) {
    int x;
    cin >> x;
    auto it = end.lower_bound(x);
    if (it == end.end()) continue;
    int r2 = *it, l2 = x + 1;
    int r1 = x - 1, l1 = start[r2];
    if (start[r2] > x) continue;
    end.erase(it);
    cnt -= (r2 - l1 + 2) / (a + 1);
    if (l1 <= r1 && (r1 - l1 + 2) / (a + 1) > 0) {
      end.insert(r1);
      start[r1] = l1;
      cnt += (r1 - l1 + 2) / (a + 1);
    }
    if (l2 <= r2 && (r2 - l2 + 2) / (a + 1) > 0) {
      end.insert(r2);
      start[r2] = l2;
      cnt += (r2 - l2 + 2) / (a + 1);
    }
    if (cnt < k) return cout << i, 0;
  }
  cout << -1 << endl;
}
