B

#include <bits/stdc++.h>

using namespace std;

#define ll     long long

int main()
{
    ll int b;
    cin>>b;

    for(ll int a=1; a<=15; a++)
    {
        ll int x = 1;

        for(int j=1; j<=a; j++)
            x *= a;

        if(x == b)
        {
            cout<<a<<"\n";
            exit(0);
        }
    }

    cout<<-1<<"\n";

}