#include <cstdio>

using namespace std;
int legendre(int n)
{
    int s=0;
    long long numitor;
    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)
    {
        dr=med-1;
        last=med;
    }
    else
    {
        st=med+1;
    }
    }
    if(legendre(last)==P)
    printf("%d",last);
    else
    printf("-1");
    return 0;
}