abc174_c.cpp

#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define fastio                      \
  ios_base::sync_with_stdio(false); \
  cin.tie(0);                       \
  cout.tie(0);
#define len(__x) (int)__x.size()
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vll = vector<ll>;
using pll = pair<ll, ll>;
using vll2d = vector<vll>;
using vi = vector<int>;
using vi2d = vector<vi>;
using pii = pair<int, int>;
using vii = vector<pii>;
using vc = vector<char>;
#define all(a) a.begin(), a.end()
#define snd second
#define fst first
#define pb(___x) push_back(___x)
#define mp(___a, ___b) make_pair(___a, ___b)
#define eb(___x) emplace_back(___x)

vector<string> dir({"LU", "U", "RU", "R", "RD", "D", "LD", "L"});
int dx[] = {-1, -1, -1, 0, 1, 1, 1, 0};
int dy[] = {-1, 0, 1, 1, 1, 0, -1, -1};
const ll oo = 1e18;

void run() {
  ll k;
  cin >> k;
  vc vis(1e6 + 1);

  ll i = 1;
  ll k10 = 7;
  ll cur = 7;
  for (;;) {
    if (vis[cur]) break;
    if (cur % k == 0) {
      cout << i << endl;
      return;
    }
    vis[cur] = true;
    k10 = (k10 * 10) % k;
    cur = (cur + k10) % k;
    i++;
  }
  cout << -1 << endl;
}
int32_t main(void) {
  fastio;
  int t;
  t = 1;
  // cin >> t;
  while (t--) run();
}

// AC, number theory