#include <fstream>
#define NMAX 1000000000
using namespace std;
long long n,suma;
long long numarzero(long long n)
{
    if(n==0) return 1;
    suma=0;
    for(long long i=5;n/i>=1;i*=5) suma+=n/i;
    return suma;
}
long long cautbin(long long n)
{
    long long st=0,dr=NMAX,m;
    while(st<=dr)
    {
        m=(st+dr)/2;
        long long zero=numarzero(m);
        if(zero==n)
        {
            long long x=m-1;
            while(numarzero(x)==zero) x--;
            return x+1;
        }
        else if(zero<n) st=m+1;
        else dr=m-1;
    }
    return -1;
}
ifstream cin("fact.in");
ofstream cout("fact.out");
int main()
{
    cin>>n;
    cout<<cautbin(n);
    return 0;
}