#include <cstdio>
using namespace std;
inline int zero(int m)
{
    int s,n=5;
    s=0;
    while(m>=n)
    {
        s+=m/n;
        n*=5;
    }
    return s;
}
int main ()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int P,st,dr,med,n;
    scanf("%d",&P);
    n=0;
    st=1;
    dr=(1u<<31)-1;
    while(st<=dr)
    {
        med=st+((dr-st)>>1);
        if (zero(med)>=P)
        {
            n=med;
            dr=med-1;
        }
        else
            st=med+1;
    }
    if (zero(n)==P)
        printf("%d\n",n);
    else
        printf("-1\n");
    return 0;
}