#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int MAXN = 1e5 + 5;
const ll linf = 0x3f3f3f3f3f3f3f3f;

struct Data {
    ll a, b;
    Data(void) {}
    Data(ll _a, ll _b): a(_a), b(_b) {}
    inline bool type(void) const {
        return a <= b;
    }
};

inline bool operator < (const Data &p, const Data &q) {
    if (p.type() != q.type())
        return p.type();

    if (p.type())
        return p.a < q.a;
    else
        return p.b > q.b;
}

inline Data operator + (const Data &p, const Data &q) {
    ll t = max(p.a, p.a - p.b + q.a);
    return Data(t, -p.a + p.b - q.a + q.b + t);
}

int n, d;
int a[MAXN];

int fa[MAXN];
inline void init(int _n) {
    for (int i = 1; i <= _n; ++i)
        fa[i] = i;
}
int find(int u) {
    return fa[u] == u ? u : fa[u] = find(fa[u]);
}
inline void connect(int u, int v) {
    fa[find(u)] = find(v);
}

pii ids[MAXN];
Data dat[MAXN];

inline bool chk(ll m) {
    if (m > 2e9)
        return 1;

    dat[d] = Data(0, m);

    for (int i = 1; i < d; ++i)
        dat[i] = Data(a[i + 1] - a[i], m);

    for (int i = d + 1; i <= n; ++i)
        dat[i] = Data(a[i] - a[i - 1], m);

    set< pair<Data, int>> t;

    for (int i = 1; i <= n; ++i)
        if (i != d)
            t.emplace(dat[i], i);

    init(n);

    while (t.size()) {
        int x = t.begin() -> second;
        t.erase(t.begin());
        int y = x < d ? find(x + 1) : find(x - 1);

        if (y != d)
            t.erase(make_pair(dat[y], y));

        dat[y] = dat[y] + dat[x];
        fa[x] = y;

        if (y != d)
            t.emplace(dat[y], y);
        else if (dat[d].a > 0)
            return 0;
    }

    return 1;
}

int main(void) {
    int m;
    scanf("%d%d%d", &n, &d, &m);

    for (int i = 1; i <= n; ++i)
        scanf("%d", &a[i]);

    if (a[1] == a[n])
        return printf("0"), 0;

    int l = 1, r = 1e9;

    while (l < r) {
        int mid = (l + r) >> 1;

        if (chk((ll)m * mid * 2))
            r = mid;
        else
            l = mid + 1;
    }

    printf("%d", l);
    return 0;
}