#include<cstdio>
using namespace std;
int p;
long long zerouri(int p)
{
    long long z=0;
    int x=5;
    while (x<=p)
    {
        z=z+p/x;
        x*=5;
    }
    return z;
}
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d ",&p);
   // printf("%lld ",zerouri(5));
    int x=1;
    while (zerouri(x)<p) x++;
    if (zerouri(x)==p) printf("%d\n",x);
        else printf("-1\n");
    return 0;
}