#include <bits/stdc++.h> 

using namespace std;

typedef long long ll;

const int N = (int)1e3 + 12;

const ll inf = 11e17;


ll b, p, d, n, a[N], dp[N][N];
ll get(ll l, ll r) {
    return r / p - (l - 1) / p;
}
ll nx(ll f) {
    return (f + p - 1) / p * p;
}
void test() {
    cin >> b >> p >> d >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    a[++n] = b;
    for(int i = 0; i <= n; i++) {
        for(int j = 0; j < p; j++) {
            dp[i][j] = inf;
        }
    }
    dp[0][0] = 0;
    for(int i = 0; i <= n; i++) {
        dp[i][0] = min(dp[i][p - 1] + 1, dp[i][0]);
        for(int j = 0; j < p; j++) {
            if(dp[i][j] == inf) continue;
            int pr = (j ? j - 1 : p - 1);
            dp[i][j] = min(dp[i][j], dp[i][pr] + 1);
            ll k = (j + a[i + 1] - a[i]) % p;
            dp[i + 1][k] = min(dp[i + 1][k], dp[i][j] + get(j + 1, j + a[i + 1] - a[i] - 1) * d + a[i + 1] - a[i]);
        }
    }
    ll res = dp[n][0];
    for(int i = 1; i < p; i++) {
        res = min(res, dp[n][i]);
    }
    cout << res << '\n';
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int t = 1;
    // cin >> t;

    while(t--) 
        test();

    return 0;
}