//#define NDEBUG
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <utility>
#include <vector>

namespace n91 {

  using i8 = std::int_fast8_t;
  using i32 = std::int_fast32_t;
  using i64 = std::int_fast64_t;
  using u8 = std::uint_fast8_t;
  using u32 = std::uint_fast32_t;
  using u64 = std::uint_fast64_t;
  using isize = std::ptrdiff_t;
  using usize = std::size_t;

  struct rep {
    struct itr {
      usize i;
      constexpr itr(const usize i) noexcept : i(i) {}
      void operator++() noexcept { ++i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    const itr f, l;
    constexpr rep(const usize f, const usize l) noexcept
      : f(std::min(f, l)), l(l) {}
    constexpr auto begin() const noexcept { return f; }
    constexpr auto end() const noexcept { return l; }
  };
  struct revrep {
    struct itr {
      usize i;
      constexpr itr(const usize i) noexcept : i(i) {}
      void operator++() noexcept { --i; }
      constexpr usize operator*() const noexcept { return i; }
      constexpr bool operator!=(const itr x) const noexcept { return i != x.i; }
    };
    const itr f, l;
    constexpr revrep(const usize f, const usize l) noexcept
      : f(l - 1), l(std::min(f, l) - 1) {}
    constexpr auto begin() const noexcept { return f; }
    constexpr auto end() const noexcept { return l; }
  };
  template <class T> auto md_vec(const usize n, const T& value) {
    return std::vector<T>(n, value);
  }
  template <class... Args> auto md_vec(const usize n, Args... args) {
    return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
  }
  template <class T> constexpr T difference(const T& a, const T& b) noexcept {
    return a < b ? b - a : a - b;
  }
  template <class T> void chmin(T& a, const T& b) noexcept {
    if (b < a)
      a = b;
  }
  template <class T> void chmax(T& a, const T& b) noexcept {
    if (a < b)
      a = b;
  }
  template <class F> class rec_lambda {
    F f;

  public:
    rec_lambda(F&& f) : f(std::move(f)) {}
    template <class... Args> auto operator()(Args&&... args) const {
      return f(*this, std::forward<Args>(args)...);
    }
  };
  template <class F> auto make_rec(F&& f) { return rec_lambda<F>(std::move(f)); }
  template <class T> T scan() {
    T ret;
    std::cin >> ret;
    return ret;
  }

} // namespace n91
#include <numeric>
namespace n91 {

  void main_() {
    /*
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    //*/
    const usize n = scan<usize>();
    const u64 m = scan<u64>();
    u64 k = scan<u64>();
    std::vector<u64> a(n);
    for (auto& e : a) {
      std::cin >> e;
    }
    if (std::accumulate(a.begin(), a.end(), static_cast<u64>(0)) <= m+k) {
      std::cout << "0\n";
      return;
    }
    std::sort(a.begin(), a.end());
    usize s = n - 1;
    u64 rem = m;
    while (true) {
      if (a[s] <= rem) {
        rem -= a[s];
        s -= 1;
      }
      else {
        break;
      }
    }
    const auto get = [](const u64 a, const u64 b) {
      return (b * (b + 1) - a * (a + 1)) / 2;
    };
    u64 ups = 0;
    for (const usize i : rep(0, s + 1)) {
      if (a[i] >= rem) {
        ups += a[i] - rem;
      }
    }
    if (ups < k) {
      k -= a[s] - rem;
      rem = 0;
      s -= 1;
    }
    u64 gt = rem, le = a[s] + 1;
    while (le - gt != 1) {
      const u64 mid = (le + gt) / 2;
      u64 sum = 0;
      for (const usize i : rep(0, s + 1)) {
        if (a[i] >= mid) {
          sum += a[i] - mid;
        }
      }
      if (sum <= k) {
        le = mid;
      }
      else {
        gt = mid;
      }
    }
    u64 ans = 0;
    for (const usize i : rep(0, s)) {
      ans += get(0, std::min(a[i], le));
    }
    ans += get(rem, le);
    u64 sum = 0;
    for (const usize i : rep(0, s + 1)) {
      if (a[i] >= le) {
        sum += a[i] - le;
      }
    }
    ans -= le * (k - sum);
    std::cout << ans << std::endl;
  }

} // namespace n91

int main() {
  n91::main_();
  return 0;
}



Measured memory_bytes: 3628