#include <queue>
#include <iostream>
#include <vector>
#include <cstring>
#include <iostream>
#include <set>
#include <cstring>
#include <stack>
#include <algorithm>
#include <map>
#include <cmath>
//#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 3e5 + 10;
const ll INF = 3e16 + 10;
string int_to_string(int x) {
    string res = "";
    while(x) {
        res += (x % 10) + '0';
        x /= 10;
    }
    reverse(res.begin(), res.end());
    return res;
}
int main() {
    ios_base::sync_with_stdio(false);
    string s;
    cin >> s;
    
    int fact = 1;
    map<string, int> mapa;
    for(int i = 1; i <= 10; i++) {
        fact *= i;
        mapa[int_to_string(fact)] = i;
    }
    if(mapa.count(s)) {
        cout << mapa[s] << endl;
        return 0;
    }
    double sum = 0;
    double sz = s.size();
    for(double i = 1; i <= 1000000; i += 1.0) {
        sum += log10(i);
        if(fabs(sz - sum) < 1.0) {
            cout << i << endl;
            return 0;
        }
    }
    return 0;
}