#include <cstdio>

using namespace std;
int legendre(int n)
{
    int s=0;
    long long k;
    k=5;
    while(k<=n)
    {
        s+=n/k;
        k=k*5;
    }
    return s;
}
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int val,st,last,dr,med,aux;
    scanf("%d",&val);
    st=1;
    last=0;
    dr=(1LL<<31)-1;
    while(st<=dr)
        {
            med=dr-(dr-st)/2;
            aux=legendre(med);
            if(aux>=val)
                {
                    last=med;
                    dr=med-1;
                }
            else
                {
                    st=med+1;
                }
        }
    if(legendre(last)==val)
        printf("%d",last);
    else
        printf("-1");
    return 0;
}