//#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 {
    if (a < b) {
      return b - a;
    }
    else {
      return 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 fix_point : private F {
  public:
    explicit constexpr fix_point(F&& f) : F(std::forward<F>(f)) {}

    template <class... Args>
    constexpr decltype(auto) operator()(Args&&... args) const {
      return F::operator()(*this, std::forward<Args>(args)...);
    }
  };
  template <class F> constexpr decltype(auto) make_fix(F&& f) {
    return fix_point<F>(std::forward<F>(f));
  }
  template <class T> T scan() {
    T ret;
    std::cin >> ret;
    return ret;
  }

} // namespace n91

#include <algorithm>
#include <iostream>
#include <string>
#include <utility>

namespace n91 {

  void main_() {
    /*
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    //*/
    const usize n = scan<usize>();
    const std::string s = scan<std::string>();
    usize ans = 0;
    for (char a = '0'; a <= '9'; a += 1) {
      for (char b = '0'; b <= '9'; b += 1) {
        for (char c = '0'; c <= '9'; c += 1) {
          std::string t = { a, b, c };
          usize i = 0;
          for (const auto e : s) {
            if (e == t[i]) {
              i += 1;
            }
            if (i == 3) {
              ans += 1;
              break;
            }
          }
        }
      }
    }
    std::cout << ans << std::endl;
    return;
  }

} // namespace n91

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


Measured memory_bytes: 256