#include <iostream>
#include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int n;

int numarul_de_zerouri(int gg){
	int cnz=0, i;
	for(int i=5;i<=gg;i*=5){
		cnz+=gg/i;
	}
	return cnz;  
}




int main(){
in >>n;
int start=1,end=1000000000,mid;
while(start<=end){
	mid=(start+end)/2;
	if(numarul_de_zerouri(mid)<n){
		start=mid+1;
	}else {
	end=mid-1;	
	}
}
if(numarul_de_zerouri(start)==n){
	out <<start;
}else{
	out <<-1;
} 
return 0;
}