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