#include<cstdio>
using namespace std;
int main(){
	FILE*f=fopen("fact.in","r");
	FILE*g=fopen("fact.out","w");
	int nr,ok,x;
	long P,m,N;
	fscanf(f,"%d", &P);
	x=-1;
	nr=0;
	N=0;
	while(nr!=P){
		N=N+5;
		ok=1;
		m=N;
		while(ok==1)
			if(m%5!=0)
				ok=0;
			else{
				nr=nr+1;
				m=m/5;
			}
	}
	if(P<1)
		fprintf(g,"%d",x);
	else 
	fprintf(g,"%d",N);
	
	fclose(f);
	fclose(g);
	}