#include<iostream>
using namespace std;
typedef long long ll;
int main(){
    ll n;
    cin>>n;
    if(n<=0){
        cout<<"-1"<<endl;
        return 0;
    }
    for(ll m=1;;m++){
        ll x=1;
        bool y=false;
        for(int i=0;i<m;i++){
            if(x>n/m){
                y=true;
                break;
            }
            x*=m;
        }
        if(y || x>n)break;
        if(x==n){
            cout<<m<<endl;
            return 0;
        }
    }
    cout<<"-1"<<endl;
    return 0;
}