#include <cstdio>
using namespace std;

int f(long long k) {
	long long nr=0;
	while (k/5!=0) {
		nr=nr+k/5;
		k=k/5;
	}
	return nr;
}
 
int main(){
	
	freopen("fact.in", "r", stdin);
	freopen("fact.out", "w", stdout);
	
    long long n,c,a=0,b=10000000000,p,r;
    scanf ("%lld", &p);
   
    c=(a+b)/2;
    while (f(c)!=p) {
    	if (f(c)<p) {
    		a=c+5;
    	}
    	else {
    		b=c-5;
    	}
    	c=(a+b)/2;
    	if (a==b) { r=-1; printf ("%d", r); break;}
    	}
    	

	if (r!=-1) {c=c-c%5; printf ("%lld", c);}
	
    return 0;
}