#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2e5 + 5;
int n, m, k, a[MAXN], op;
bool vis[MAXN];
bool check(int x) {
  memset(vis, 0, sizeof(vis));
  for (int i = 1; i <= x; i++) {
    vis[a[i]] = 1;
  }
  int last = 1, ans = 0;
  for (int i = 1; i <= n; i++) {
    if (vis[i]) {
      continue;
    }
    int tmp = 1;
    while (!vis[i + 1] && i + 1 <= n) {
      i++;
      tmp++;
    }
    ans += (tmp + 1) / (k + 1);
  }
  return ans < m;
}
int main() {
  scanf("%d%d%d", &n, &m, &k);
  scanf("%d", &op);
  for (int i = 1; i <= op; i++) {
    scanf("%d", &a[i]);
  }
  int l = 1, r = op + 1;
  while (l <= r) {
    if (l > op) {
      break;
    }
    int mid = (l + r) >> 1;
    if (check(mid)) {
      r = mid - 1;
    } else {
      l = mid + 1;
    }
  }
  printf("%d\n", l > op ? -1 : l);
  return 0;
}
