#include<cstdio>
#include<algorithm>
using namespace std;
int n,i,j,p,st,dr,m,x,minn;
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    st=1; dr=100000000; minn=100000000;
    while (st<=dr)
    {
        m=(st+dr)/2; x=5; n=0;
        while (m>=x)
        n=n+(m/x),x=x*5;
        if (n==p) minn=min(m,minn);
        if (n<p) st=m+1; else dr=m-1;
    }
    if (minn==100000000) minn=-1;
    printf("%d",minn);
    return 0;
}