#include <bits/stdc++.h>
using namespace std;
unordered_map<int, int> mp;
int n;
int mi = INT_MAX;
void dfs(long long num){
	string s = to_string(num);
 
	if(s.size() >= n){
		mi = min(mi, mp[num]);
		return;
	}
	for(int i = 0; i < s.size(); i++){
		if(mp[(s[i] - '0') * num] || s[i] - '0' == 1) continue;
		mp[(s[i] - '0') * num] = mp[num] + 1; 
		dfs((s[i] - '0') * num);
	}
 
}
signed main(){
	long long x;
	cin >> n >> x;
	dfs(x);
	if(mi == INT_MAX){
		cout << -1;
	}else cout << mi;
}

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