#include <cstdio>
using namespace std;
int n,min,max,i;
int verif(int m){
    int nr=0;
    while(m>=5){
        m/=5;
        nr+=m;}
    return nr;
}
int main(){
	freopen ("fact.in","r",stdin);
	freopen ("fact.out","w",stdout);
    scanf ("%d",&n);
	/*	while (nr<27){ x=x*2; nr++;} 
	for (i=0;x!=0;x=x/2)
		if (verif(i+x)) i=i+x;*/
    if(n==0) printf ("1");
     min=1; max=1000000000;
    while(min<max){
        int mij=min+(max-min)/2;
        if(verif(mij)>=n) max=mij;
        else min=mij+1;
    }
    if(verif(min)==n) printf ("%d",min);
    else printf ("-1");
    return 0;
}