#include <cstdio>
using namespace std;
int zero(int x)
{
    int s=0,numitor=5;
    while(x/numitor>0)
    {
        s+=x/numitor;
        numitor*=5;
    }
    return s;
}
int bs_left (int st,int dr,int val)
{
    int med,last,zerou;

    last=-1;
    while(st<=dr)
    {
        med=st+(dr-st)/2;
        zerou=zero(med);
            if(val<=zerou)
                {
                    dr=med-1;
                    //if(last==val)
                    last=med;
                }
            else
                st=med+1;
    }
    return last;
}
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int n,x;
    scanf("%d",&n);
    x=bs_left(1,1000000000,n);
    if(zero(x)==n)
        printf("%d",x);
    else
        printf("-1");
    return 0;
}