#pragma region template
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vld = vector<ld>;
using vvld = vector<vld>;
using vvvld = vector<vvld>;
using vs = vector<string>;
using pll = pair<ll, ll>;
using vp = vector<pll>;
template <typename T> using pqrev = priority_queue<T, vector<T>, greater<T>>;
#define rep(i, n) for (ll i = 0, i##_end = (n); i < i##_end; i++)
#define repb(i, n) for (ll i = (n)-1; i >= 0; i--)
#define repr(i, a, b) for (ll i = (a), i##_end = (b); i < i##_end; i++)
#define reprb(i, a, b) for (ll i = (b)-1, i##_end = (a); i >= i##_end; i--)
#define ALL(a) (a).begin(), (a).end()
#define SZ(x) ((ll)(x).size())
//*
constexpr ll MOD = 1e9 + 7;
/*/
constexpr ll MOD = 998244353;
//*/
constexpr ll INF = 1e+18;
constexpr ld EPS = 1e-12L;
constexpr ld PI = 3.14159265358979323846L;
constexpr ll GCD(ll a, ll b) { return b ? GCD(b, a % b) : a; }
constexpr ll LCM(ll a, ll b) { return a / GCD(a, b) * b; }
template <typename S, typename T> constexpr bool chmax(S &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename S, typename T> constexpr bool chmin(S &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
#ifdef OJ_LOCAL
#include "dump.hpp"
#else
#define dump(...) ((void)0)
#endif
template <typename T> bool print_(const T &a) {
  cout << a;
  return true;
}
template <typename T> bool print_(const vector<T> &vec) {
  for (auto &a : vec) {
    cout << a;
    if (&a != &vec.back()) {
      cout << " ";
    }
  }
  return false;
}
template <typename T> bool print_(const vector<vector<T>> &vv) {
  for (auto &v : vv) {
    for (auto &a : v) {
      cout << a;
      if (&a != &v.back()) {
        cout << " ";
      }
    }
    if (&v != &vv.back()) {
      cout << "\n";
    }
  }
  return false;
}
void print() { cout << "\n"; }
template <typename Head, typename... Tail>
void print(Head &&head, Tail &&... tail) {
  bool f = print_(head);
  if (sizeof...(tail) != 0) {
    cout << (f ? " " : "\n");
  }
  print(forward<Tail>(tail)...);
}
#pragma endregion

ll inverse(ll x, ll r){
  ll a = x, b = r, u = 1, v = 0, t;
  while (b > 0) {
    t = a / b;
    swap(a -= t * b, b);
    swap(u -= t * v, v);
  }
  return (u + r) % r;
};

// min x >= 0, g^x % mod == h
ll babystep_giantstep(ll g, ll h, ll mod) {
  const auto powmod = [](ll a, ll b, ll r) {
    ll ans = 1;
    ll tmp = a;
    while (b) {
      if (b & 1) {
        ans = (ans * tmp) % r;
      }
      tmp = (tmp * tmp) % r;
      b >>= 1;
    }
    return ans;
  };
  const auto inv = [](ll x, ll r){
    ll a = x, b = r, u = 1, v = 0, t;
    while (b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return (u + r) % r;
  };
  const ll m = ceil(sqrt(mod));
  unordered_map<ll, ll> table;
  ll e = 1;
  for (ll i = 0; i < m; i++) {
    if (!table.count(e)) table[e] = i;
    e = (e * g) % mod;
  }
  const ll factor = powmod(inv(g, mod), m, mod);
  e = h;
  for (ll i = 0; i < m; i++) {
    if (table.count(e)) {
      return i*m + table[e];
    }
    e = (e * factor) % mod;
  }
  return -1;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  ll k;
  cin >> k;
  if(k == 1 || k == 7){
    print(1);
    return 0;
  }
  if(k%2 == 0 || k%5==0){
    print(-1);
    return 0;
  }
  k = k%7==0 ? k/7 : k;
  k *= 9;
  ll ans = babystep_giantstep(10, inverse(10, k), k);
  print(ans == -1 ? -1 : ans+1);
}


Measured memory_bytes: 3876