#include<stdio.h>
int ver(long i,long p)
{
int s=0,num=5;
while(i/num)
{
s+=i/num;
num*=5;
}
if(s==p)
return 1;
return 0;
}
int main()
{
long p,li,ls,i;
freopen("fact.in","r",stdin);
freopen("fact.out","w",stdout);
scanf("%d",&p);
if(p)
{
li=p<<2;
ls=5*p;
for(i=li;i<=ls;i++)
if(ver(i,p))
{
printf("%ld",i);
return 0;
}
printf("-1");
}
else
printf("1");
fcloseall();
return 0;
}