#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 4005, inf = 1e9;
int dp[MAX_N], cnt[MAX_N];
int n, D, T;
// i can activate [i, nxt[i])
int s[MAX_N], nxt[MAX_N];
pair<int,int> solve_dp(int cost) {
vector<int> ok(n + 10), cur_nxt(n + 10);
int cnt1 = 0;
for (int i = n;i >= 1;--i) {
for (int j = i;j < nxt[i];++j) {
if (ok[j]) j = cur_nxt[j] - 1;
else ok[j] = true, ++cnt1;
}
cur_nxt[i] = ok[ nxt[i] ] ? cur_nxt[ nxt[i] ] : nxt[i];
dp[i] = cnt1 + cost;
//dp[i] = accumulate(begin(ok)+i, end(ok), 0) + cost;
cnt[i] = 1;
int sum = 0;
for (int k = i+1;k <= n;++k) {
sum += ok[k-1];
if (chmin(dp[i], cost + sum + dp[k]))
cnt[i] = cnt[k]+1;
if (dp[i] == cost + sum + dp[k])
chmin(cnt[i], cnt[k]+1);
}
}
return make_pair(cnt[1], dp[1]);
}
int32_t main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> n >> D >> T; ++D;
// Just to be faster
assert(n < MAX_N);
for (int i = 1;i <= n;++i) {
cin >> s[i];
nxt[i] = min(n+1, max(i, i + T - s[i] + 1));
}
int l = 0, r = n, mid;
while (l < r) {
mid = l + r >> 1;
auto [c, w] = solve_dp(mid);
if (c > D)
l = mid+1;
else
r = mid;
}
auto [c, w] = solve_dp(l);
cout << w - l * D << '\n';
}
