コード
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template <typename T>
std::ostream& operator<<(std::ostream& out, const std::vector<T>& v) {
if (!v.empty()) {
out << '[';
std::copy(v.begin(), v.end(), std::ostream_iterator<T>(out, ", "));
out << "\b\b]";
}
return out;
}
vector<ll> goods;
ll dfs(ll n, ll cnt, ll k) {
if (n == 1) return cnt;
if (n % 2 == 1) return -1;
for (int i = k; i < goods.size(); i++) {
ll v = goods[i];
if (v > n) break;
if (n % v == 0) {
ll d = dfs(n / v, cnt + 1, i);
if (d > 0) return d;
}
}
return -1;
}
int main() {
cin.tie(0);
ios::sync_with_stdio(false);
ll N;
cin >> N;
if (N == 1) {
cout << -1 << endl;
return 0;
}
queue<ll> que;
goods.push_back(2);
goods.push_back(8);
que.push(2);
que.push(8);
ll a = 10;
while (!que.empty()) {
ll p = que.front();
que.pop();
if (p > N) break;
while (a < p) a *= 10;
goods.push_back(a * 2 + p);
goods.push_back(a * 8 + p);
que.push(a * 2 + p);
que.push(a * 8 + p);
}
sort(goods.begin(), goods.end());
cout << dfs(N, 0, 0) << endl;
}
