#include <cstdio>
using namespace std;
int n,inc,sf,x,mij,nrzero;
int zero(int n)
{
    int nz=0;
    for(int i=5;i<=n;i*=5)
        nz+=(n/i);
    return nz;
}
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d ",&n);
    if(n==0)
    {
        printf("1\n");
        return 0;
    }
    inc=1,sf=100000000,x=-1;
    while(inc<=sf)
    {
        mij=(sf+inc)/2;
        nrzero=zero(mij);
        if(nrzero==n)
        {
            x=mij;
            inc=sf+1;
        }
        else if(nrzero>n)
            sf=mij-1;
        else
        {
            if(nrzero<n)
                inc=mij+1;
            else sf--;
        }
    }
    printf("%d\n",x);
    return 0;
}