#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
const double eps = 1e-9;
const int INF = 1E9;
const int MAXN = 211111;
int n, k, a, m, L, M, R, curMax;
set<pair<int, int> > segments;
int countNum(int len) {
  if (len < a) return 0;
  return (len - a) / (a + 1) + 1;
}
int main() {
  scanf("%d%d%d", &n, &k, &a);
  segments.insert({n - 1, n});
  curMax = countNum(n);
  scanf("%d", &m);
  for (int i = 0; i < (int)(m); i++) {
    scanf("%d", &M);
    M--;
    auto cur = *segments.lower_bound({M, -INF});
    curMax -= countNum(cur.second);
    R = cur.first;
    L = cur.first - cur.second + 1;
    if (M - L > 0) {
      pair<int, int> cur1 = {M - 1, M - L};
      curMax += countNum(cur1.second);
      segments.insert(cur1);
    }
    if (R - M > 0) {
      pair<int, int> cur2 = {R, R - M};
      curMax += countNum(cur2.second);
      segments.insert(cur2);
    }
    if (curMax < k) {
      cout << i + 1;
      return 0;
    }
  }
  cout << -1;
  return 0;
}
