#include <iostream>
#include <cmath>

using namespace std;

int main(){

    long long a,ans=1001001001001001;
    cin>>a;
    
    for(long long n=2;n<=101;n++){
        long long m=ceil(log(a)/log(n));
        ans=min(ans,n*m);
    }
    cout<<ans<<endl;

    return 0;
}