#include "bits/stdc++.h"

using namespace std;

unsigned long long b;

unsigned long long asd(unsigned long long x){

	int ans=1;
    
	for(unsigned long long i=1;i<=x;i++){
    
		ans*=x;
        
	}
    
	return ans;
    
}

int main(){

	cin>>b;
    
	for(unsigned long long i=1;i<=15;i++){
    
		if(asd(i)==b){
        
			cout<<i;
            
			return 0;
            
		}
        
	}
    
	cout<<"-1";
    
}