// Author: Tyler Wang

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdlib>
#include <deque>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <map>
#include <memory>
#include <numeric>
#include <optional>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <string_view>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>

using namespace std;

template <class C>
constexpr auto ssize(const C& c)
    -> std::common_type_t<std::ptrdiff_t,
                          std::make_signed_t<decltype(c.size())>> {
  using R = std::common_type_t<std::ptrdiff_t,
                               std::make_signed_t<decltype(c.size())>>;
  return (R)c.size();
}

template <class T, std::ptrdiff_t N>
constexpr std::ptrdiff_t ssize(const T (&)[N]) noexcept {
  return N;
}

template <typename T>
constexpr std::enable_if_t<std::is_unsigned_v<T>, bool> has_single_bit(
    T x) noexcept {
  return x != 0 && (x & (x - 1)) == 0;
}

template <typename T>
constexpr std::enable_if_t<std::is_unsigned_v<T>, int> countl_zero(
    T x) noexcept {
  if constexpr (sizeof(T) <= sizeof(unsigned)) {
    return __builtin_clz(x) - (std::numeric_limits<unsigned>::digits -
                               std::numeric_limits<T>::digits);
  } else if constexpr (sizeof(T) <= sizeof(unsigned long)) {
    return __builtin_clzl(x) - (std::numeric_limits<unsigned long>::digits -
                                std::numeric_limits<T>::digits);
  } else {
    static_assert(sizeof(T) <= sizeof(unsigned long long));
    return __builtin_clzll(x) -
           (std::numeric_limits<unsigned long long>::digits -
            std::numeric_limits<T>::digits);
  }
}

template <typename T>
constexpr std::enable_if_t<std::is_unsigned_v<T>, int> countr_zero(
    T x) noexcept {
  if constexpr (sizeof(T) <= sizeof(unsigned)) {
    return __builtin_ctz(x);
  } else if constexpr (sizeof(T) <= sizeof(unsigned long)) {
    return __builtin_ctzl(x);
  } else {
    static_assert(sizeof(T) <= sizeof(unsigned long long));
    return __builtin_ctzll(x);
  }
}

template <typename T>
constexpr std::enable_if_t<std::is_unsigned_v<T>, int> popcount(T x) noexcept {
  if constexpr (sizeof(T) <= sizeof(unsigned)) {
    return __builtin_popcount(x);
  } else if constexpr (sizeof(T) <= sizeof(unsigned long long)) {
    return __builtin_popcountl(x);
  } else {
    static_assert(sizeof(T) <= sizeof(unsigned long long));
    return __builtin_popcountll(x);
  }
}

template <typename T>
constexpr std::enable_if_t<std::is_unsigned_v<T>, T> bit_width(T x) noexcept {
  return (T)(std::numeric_limits<T>::digits - countl_zero(x));
}

template <typename T>
constexpr std::enable_if_t<std::is_unsigned_v<T>, T> bit_ceil(T x) noexcept {
  return (T)(x <= 1 ? 1 : (T)1 << bit_width((T)(x - 1)));
}

template <typename T>
constexpr std::enable_if_t<std::is_unsigned_v<T>, T> bit_floor(T x) noexcept {
  return (T)(x == 0 ? 0 : (T)1 << (bit_width(x) - 1));
}

#if defined(__GNUC__) && !defined(__clang__)

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

template <typename Key, typename Compare = std::less<Key>,
          typename Allocator = std::allocator<Key>>
using ordered_set =
    __gnu_pbds::tree<Key, __gnu_pbds::null_type, Compare,
                     __gnu_pbds::rb_tree_tag,
                     __gnu_pbds::tree_order_statistics_node_update, Allocator>;

template <typename Key, typename T, typename Compare = std::less<Key>,
          typename Allocator = std::allocator<std::pair<const Key, T>>>
using ordered_map =
    __gnu_pbds::tree<Key, T, Compare, __gnu_pbds::rb_tree_tag,
                     __gnu_pbds::tree_order_statistics_node_update, Allocator>;

#endif

template <typename Fun>
class y_combinator_result {
 public:
  template <typename T>
  explicit y_combinator_result(T&& fun) : fun_(std::forward<T>(fun)) {}

  template <typename... Args>
  decltype(auto) operator()(Args&&... args) {
    return fun_(std::ref(*this), std::forward<Args>(args)...);
  }

 private:
  Fun fun_;
};

template <typename Fun>
decltype(auto) y_combinator(Fun&& fun) {
  return y_combinator_result<std::decay_t<Fun>>(std::forward<Fun>(fun));
}

template <typename T>
std::ostream& operator<<(std::ostream& os, const std::optional<T>& opt);

template <typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, const std::pair<T1, T2>& p);

template <typename... Ts>
std::ostream& operator<<(std::ostream& os, const std::tuple<Ts...>& t);

template <typename Container,
          std::enable_if_t<!std::is_convertible_v<Container, std::string_view>,
                           typename Container::const_iterator>* = nullptr>
std::ostream& operator<<(std::ostream& os, const Container& c);

template <typename ContainerAdaptor,
          typename ContainerAdaptor::container_type* = nullptr>
std::ostream& operator<<(std::ostream& os, const ContainerAdaptor& a);

template <typename T>
std::ostream& operator<<(std::ostream& os, const std::optional<T>& opt) {
  return opt ? os << *opt : os << "nullopt";
}

template <typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, const std::pair<T1, T2>& p) {
  return os << '{' << p.first << ", " << p.second << '}';
}

template <typename... Ts>
std::ostream& operator<<(std::ostream& os, const std::tuple<Ts...>& t) {
  return std::apply(
      [&os](const Ts&... args) -> std::ostream& {
        os << '{';
        int i = 0;
        ((os << (i++ == 0 ? "" : ", ") << args), ...);
        return os << '}';
      },
      t);
}

template <typename Container,
          std::enable_if_t<!std::is_convertible_v<Container, std::string_view>,
                           typename Container::const_iterator>*>
std::ostream& operator<<(std::ostream& os, const Container& c) {
  os << '{';
  for (auto it = c.begin(); it != c.end(); ++it) {
    os << (it == c.begin() ? "" : ", ") << *it;
  }
  return os << '}';
}

template <typename ContainerAdaptor, typename ContainerAdaptor::container_type*>
std::ostream& operator<<(std::ostream& os, const ContainerAdaptor& a) {
  class subadaptor : public ContainerAdaptor {
   public:
    const auto& c() const { return ContainerAdaptor::c; }
  };
  return os << static_cast<const subadaptor&>(a).c();
}

namespace detail {

template <typename... Ts>
void print(std::ostream& os, int line, std::string_view keys,
           const Ts&... vals) {
  if constexpr (sizeof...(Ts) == 0) {
    os << "  " << line << " |" << std::endl;
  } else {
    std::vector<std::string_view> key_list;
    key_list.reserve(sizeof...(Ts));
    int start = 0, paren = 0;
    for (int i = 0; i < (int)keys.size(); ++i) {
      switch (keys[i]) {
        case '(':
        case '[':
        case '{':
          ++paren;
          break;
        case ')':
        case ']':
        case '}':
          --paren;
          break;
        case ',':
          if (paren == 0) {
            key_list.push_back(keys.substr(start, i - start));
            start = i;
          }
          break;
      }
    }
    key_list.push_back(keys.substr(start));
    assert(key_list.size() == sizeof...(Ts));
    os << "  " << line << " | ";
    int i = 0;
    ((os << key_list[i++] << " = " << vals), ...);
    os << std::endl;
  }
}

}  // namespace detail

#ifdef TYLER
#define debug(...) \
  detail::print(std::cerr, __LINE__, #__VA_ARGS__ __VA_OPT__(, ) __VA_ARGS__)
#else
#define debug(...) ((void)0)
#endif

int MODULUS = 1'000'000'007;

template <const int& Modulus = MODULUS>
class mod_int {
 public:
  constexpr mod_int() : val_(0) {}

  template <typename T>
  constexpr mod_int(T val) : val_((int)(val % Modulus)) {
    static_assert(std::is_integral_v<T>);
    if (val_ < 0) {
      val_ += Modulus;
    }
  }

  static constexpr int modulus() { return Modulus; }

  template <typename T>
  constexpr explicit operator T() const {
    return (T)val_;
  }

  constexpr mod_int& operator++() {
    if (++val_ == Modulus) {
      val_ = 0;
    }
    return *this;
  }

  constexpr mod_int operator++(int) {
    mod_int t = *this;
    ++*this;
    return t;
  }

  constexpr mod_int& operator--() {
    if (val_ == 0) {
      val_ = Modulus;
    }
    --val_;
    return *this;
  }

  constexpr mod_int operator--(int) {
    mod_int t = *this;
    --*this;
    return t;
  }

  constexpr mod_int& operator+=(mod_int other) {
    if ((val_ += other.val_) >= Modulus) {
      val_ -= Modulus;
    }
    return *this;
  }

  constexpr mod_int& operator-=(mod_int other) {
    if ((val_ -= other.val_) < 0) {
      val_ += Modulus;
    }
    return *this;
  }

  constexpr mod_int& operator*=(mod_int other) {
    val_ = (int)((long long)val_ * other.val_ % Modulus);
    return *this;
  }

  constexpr mod_int& operator/=(mod_int other) { return *this *= inv(other); }

  friend constexpr mod_int operator+(mod_int mi) { return mi; }

  friend constexpr mod_int operator-(mod_int mi) {
    if (mi.val_ != 0) {
      mi.val_ = Modulus - mi.val_;
    }
    return mi;
  }

  friend constexpr mod_int operator+(mod_int lhs, mod_int rhs) {
    return lhs += rhs;
  }

  friend constexpr mod_int operator-(mod_int lhs, mod_int rhs) {
    return lhs -= rhs;
  }

  friend constexpr mod_int operator*(mod_int lhs, mod_int rhs) {
    return lhs *= rhs;
  }

  friend constexpr mod_int operator/(mod_int lhs, mod_int rhs) {
    return lhs /= rhs;
  }

  friend constexpr bool operator==(mod_int lhs, mod_int rhs) {
    return lhs.val_ == rhs.val_;
  }

  friend constexpr bool operator!=(mod_int lhs, mod_int rhs) {
    return lhs.val_ != rhs.val_;
  }

  friend constexpr bool operator<(mod_int lhs, mod_int rhs) {
    return lhs.val_ < rhs.val_;
  }

  friend constexpr bool operator<=(mod_int lhs, mod_int rhs) {
    return lhs.val_ <= rhs.val_;
  }

  friend constexpr bool operator>(mod_int lhs, mod_int rhs) {
    return lhs.val_ > rhs.val_;
  }

  friend constexpr bool operator>=(mod_int lhs, mod_int rhs) {
    return lhs.val_ >= rhs.val_;
  }

  friend std::ostream& operator<<(std::ostream& os, mod_int mi) {
    return os << mi.val_;
  }

  friend std::istream& operator>>(std::istream& is, mod_int& mi) {
    long long val;
    is >> val;
    mi = mod_int(val);
    return is;
  }

  friend constexpr mod_int inv(mod_int mi) {
    int a = mi.val_, b = Modulus;
    int x = 0, xx = 1;
    while (a != 0) {
      int q = b / a;
      int t = a;
      a = b - q * a;
      b = t;
      t = xx;
      xx = x - q * xx;
      x = t;
    }
    return mod_int(x);
  }

  template <typename T>
  friend constexpr mod_int pow(mod_int base, T expo) {
    static_assert(std::is_integral_v<T>);
    if (expo < 0) {
      base = inv(base);
      expo = -expo;
    }
    mod_int power = 1;
    for (; expo != 0; expo >>= 1) {
      if (expo & 1) {
        power *= base;
      }
      base *= base;
    }
    return power;
  }

 private:
  int val_;
};

int main() {
  auto start_time = std::chrono::steady_clock::now();
  std::mt19937 thanos(
      (std::uint_fast32_t)start_time.time_since_epoch().count());
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  std::cout.precision(24);
  cin >> MODULUS;
  mod_int<> seven = 0;
  for (long long i = 0; i < MODULUS; ++i) {
    seven = 10 * seven + 7;
    if (seven == 0) {
      cout << i + 1 << '\n';
      return 0;
    }
  }
  cout << -1 << '\n';
  return 0;
}

Measured memory_bytes: 3624