#include <bits/stdc++.h>
#define mid ((l+r)/2)
using namespace std;
const int MAXN = 100010;
const int MAXK = 15;
const int INF = 1000000000;
int N, L, K;
set<int> s;
map<int, int> mp;

int seg[4*MAXN], lazy[4*MAXN], h[MAXN], dp[MAXN][MAXK];

void init1(int node, int l, int r) {
    seg[node] = 0;
    lazy[node] = 0;
    if (l != r) {
        init1(2*node, l, mid);
        init1(2*node+1, mid+1, r);
    }
}
void init2(int node, int l, int r) {
    seg[node] = INF;
    lazy[node] = 0;
    if (l != r) {
        init2(2*node, l, mid);
        init2(2*node+1, mid+1, r);
    }
}

void propagate(int node, int l, int r) {
    if (lazy[node]) {
        seg[node] += lazy[node];
        if (l != r) {
            lazy[2*node] += lazy[node];
            lazy[2*node+1] += lazy[node];
        }
        lazy[node] = 0;
    }
}

void update(int node, int l, int r, int L, int R, int val) {
    propagate(node, l, r);
    if (L <= l && r <= R) {
        lazy[node] += val;
        propagate(node, l, r);
        return;
    }
    if (L <= mid) update(2*node, l, mid, L, R, val);
    if (R >  mid) update(2*node+1, mid+1, r, L, R, val);
    seg[node] = min(seg[2*node], seg[2*node+1]);
}

int query(int node, int l, int r, int L, int R) {
    propagate(node, l, r);
    if (R < L || r < l || R < l || r < L) {
        //cerr << "OUT: " << node << ' ' << l << ' ' << r << ' ' << L << ' ' << R << endl;
        return INF;
    }
    if (L <= l && r <= R) {
        //cerr << "SEG: " << node << ' ' << l << ' ' << r << ' ' << L << ' ' << R << ' ' << seg[node] << endl;
        return seg[node];
    }
    return min(query(2*node, l,  mid, L, R), query(2*node+1, mid+1, r, L, R));
}

int main() {
    cin >> N >> L >> K;
    for (int i = 1; i <= N; i++) {
        cin >> h[i];
        s.insert(h[i]);
    }
    int sol = 0;
    for (int i = 1; i < L; i++) {
        if (h[i] >= h[L]) sol++;
    }
    int idxx = 1;
    for (auto x : s) {
        mp[x] = idxx;
        idxx++;
    }
    for (int i = 1; i <= N+1; i++) {
        h[i] = mp[h[i]];
        //cout << h[i] << ' ';
        dp[i][0] = INF;
    }
    for (int k = 1; k <= K; k++) {
        if (k == 1) init1(1, 1, N);
        else init2(1, 1, N);
        for (int i = N; i >= 1; i--) {
            //cerr << "K=" << k << endl;
            //cerr << "BANAN1" << endl;
            dp[i][k] = (h[i] == N ? (k==1 ? 0:INF):query(1, 1, N, h[i]+1, N));
            //cerr << i << ' ' << k << ' ' << dp[i][k] << endl;
            //cerr << "BANAN2" << endl;
            update(1, 1, N, 1, h[i], +1);
            //cerr << "BANAN3" << endl;
            int temp = query(1, 1, N, h[i], h[i]);
            //cerr << "BANAN4" << endl;
            if (dp[i][k-1] < temp) update(1, 1, N, h[i], h[i], dp[i][k-1]-temp);
        }
    }
    //cerr << sol << ' ' << dp[L][K] << endl;
    cout << (dp[L][K]+sol >= INF ? -1 : dp[L][K]+sol);
    return 0;
}