#include <cstdio>
int zero(int n)
{
int p=5,nr=0;
while(n/p>0){nr+=n/p; p*=5;}
return nr;
}
int cbin(int p)
{
int l=1,r=(1<<31)-1,m;
while(l<r)
{
m=((long long)l+r)/2;
if(zero(m)>=p)r=m; else l=m+1;
}
if(zero(r)==p)return r;
return -1;
}
int main()
{
int p;
freopen("fact.in","r",stdin);
freopen("fact.out","w",stdout);
scanf("%d",&p);
printf("%d\n",cbin(p));
return 0;

}