#include <fstream>
#include <climits>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int legendre(long long n)
{
    int p=5;
    int e=0;
    long long numitor=p;
    while(n>=numitor)
    {
        e=e+n/numitor;
        numitor=numitor*p;
    }
    return e;
}
long long bsL(long long st,long long dr,long long k)
{
    long long med,exp;
    while(st<=dr)
    {
        med=(st+dr)/2;
        exp=legendre(med);
        if(k<=exp)
            dr=med-1;
        else
            st=med+1;
    }
    return st;
}
int main()
{
    long long p,n;
    fin>>p;
    n=bsL(1,LLONG_MAX,p);
    fout<<n;
    return 0;
}