#include<iostream>

#include<cstdio>

#include<cstring>

#include<set>

using namespace std;

int L,N,a,M;

int main()

{

    set<int> Pos;

    set<int>::iterator it;

    cin >> L >> N >> a;

    {

        Pos.clear();

        Pos.insert(0),Pos.insert(L+1);

        int ans =1 + (L - a) / (a + 1);

        cin >> M;

        for(int i = 1; i <= M; ++i)

        {

            int x;

            cin >> x;

            it = Pos.lower_bound(x);

            int r = *it - 1;

            int l = *(--it) + 1;

            int len = r - l + 1;

            int Sum = 0, SumR = 0, SumL = 0;

            if(len >= a)

                Sum = 1 + (len - a) / (a + 1);

            if(x - l >= a)

                SumL = 1 + (x - l - a) / (a + 1);

            if(r - x >= a)

                SumR = 1 + (r - x - a) / (a + 1);

            ans = ans - Sum + SumL + SumR;

            if(ans < N) {

                cout << i << endl;

                return 0;

            }

            Pos.insert(x);

        }

        cout << "-1\n";

    }

    return 0;

 }