//
//  main.cpp
//  Factorial
//
//  Created by Nagy Dani on 2014.02.27..
//  Copyright (c) 2014 Nagy Dani. All rights reserved.
//

#include <cstdio>
#include <cstdlib>
#include <set>
int p;
int n;
class NUM{
public:
    long sz;
    int szj;
    void setszj();
};
void NUM::setszj(){
    long k = this->sz,i = 0;
    for (;k != 0 ; k/=10, i++);
    this->szj = i;
}

/*
class cmp{
    bool operator() (NUM a,NUM b){
        return a.szj < b.szj ? true : false;
    }
};

std::set<NUM,cmp> numbers;
*/

void read(){
    FILE* in = fopen("fact.in","r");
    fscanf(in, "%d",&p);
}
long factor(int k){
    long retv = 1;
    for (int i = 2; i <= k; i++) {
        retv*=i;
    }
    return retv;
}
void solve(){
    NUM k;
    n = 0;
    while (k.szj != p) {
        k.sz = factor(n);
        k.setszj();
        n++;
    }
    FILE* out = fopen("fact.out", "w");
    fprintf(out, "%d",n);
}
int main(int argc, const char * argv[])
{
    //printf("%ld",factor(4));
    read();
    solve();
}