#include <bits/stdc++.h>
#define SZ(x) (int) x.size() - 1
#define all(x) x.begin(), x.end()
#define ms(x, y) memset(x, y, sizeof x)
#define F(i, x, y) for (int i = (x); i <= (y); i++)
#define DF(i, x, y) for (int i = (x); i >= (y); i--)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
template <typename T> void chkmax(T& x, T y) { x = max(x, y); }
template <typename T> void chkmin(T& x, T y) { x = min(x, y); }
template <typename T> void read(T &x) {
	x = 0; int f = 1; char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;
	for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
	x *= f;
}
const int N = 1e5 + 10;
int n, m, a[N], l[N];
ll k, s;
bool check(int x) {
	ll sum = 0;
	F(i, 1, n) sum += max(0, a[i] - max(l[i], x) + 1);
	return sum <= k;
}
signed main() {
	read(n); read(m); read(k);
	F(i, 1, n) read(a[i]);
	sort(a + 1, a + n + 1);
	ll ans = 0;
	DF(i, n, 1) {
		// cout << s << " " << a[i] << " " << k << endl;
		if (s + a[i] <= m) {
			s += a[i];
			n--;
		} else {
			l[i] = m - s + 1;
			ans += (ll) (l[i] + a[i]) * (a[i] - l[i] + 1) / 2;
			// cout << l[i] << " " << a[i] << endl;
			s = m;
		}
	}
	// cout << ans << endl;
	int l = -1, r = m + 1;
	while (l + 1 < r) {
		int mid = (l + r) >> 1;
		if (check(mid)) r = mid;
		else l = mid;
	}
	ll sum = 0;
	F(i, 1, n) {
		int k = max(::l[i], r);
		if (k <= a[i]) {
			sum += a[i] - k + 1;
			ans -= (ll) (a[i] + k) * (a[i] - k + 1) / 2;
		}
		chkmin(a[i], r - 1);
	}
	F(i, 1, n) {
		if (sum < k && a[i] == r - 1 && a[i] >= ::l[i]) {
			sum++;
			ans -= r - 1;
		}
	} cout << ans;
	return 0;
}