#include <bits/stdc++.h>
using namespace std;
const double
        pi = 3.14159265358979323846,
        e = 2.7182818284590452354;
int main(){
    string s;
    cin>>s;
    if(s=="1"){
        cout<<1;
        return 0;
    }
    int a;
    if(s.size()<4){
        a=atoi(s.c_str());
        int ans=2;
        while(a!=1){
            a/=ans;
            ans++;
        }
        cout<<ans-1;
        return 0;
    }
    for(int n=1;n<=2000;n++){
        a=ceil(log10(2 * pi * n) / 2 + n * (log10(n / e)));
        if(s.size()==a){
            cout<<n;
            return 0;
        }
    }

}