#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, i, j,c,a=0,b=10000000000,p;
    scanf ("%lld", &p);
    //printf ("%lld", f(15));
    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) {printf ("%d", -1); break; break;}
    	}
    	

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