#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, k, a, i, j, x, y, xx, yy, m, p, s;
  cin >> n >> k >> a >> m;
  set<pair<int, int>> ss;
  set<pair<int, int>>::iterator it;
  ss.insert({1, n});
  s = (n + 1) / (a + 1);
  bool found = false;
  for (i = 1; i <= m; i++) {
    cin >> p;
    it = ss.lower_bound({p + 1, 0});
    if (it == ss.begin()) continue;
    it--;
    x = it->first;
    y = it->second;
    if ((p >= x) && (p <= y)) {
      s -= (y - x + 2) / (a + 1);
      ss.erase({x, y});
      if (p > x) {
        ss.insert({x, p - 1});
        s += (p - 1 - x + 2) / (a + 1);
      }
      if (p < y) {
        ss.insert({p + 1, y});
        s += (y - (p + 1) + 2) / (a + 1);
      }
    }
    if (s < k) {
      found = true;
      cout << i << "\n";
      break;
    }
  }
  if (!found) cout << "-1\n";
  return 0;
}
