#include <bits/stdc++.h>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
unsigned long long n,i,r,li,ls,z,m,nrzero;
long long NR;
int nrz(unsigned long long M)
{
    long long k,nrzero;
    nrzero = 0;
    for(i=5;i<=M;i*=5)
        nrzero+=M/i;
    return nrzero;
}
int cb(unsigned long long x, unsigned long long y)
{
    long long af = 0;
    li = x;
    ls = y;
    int OK = 0;
    while(li <= ls)
    {
        m = (li+ls)/2;
        NR = nrz(m);
        if(NR == n)
            af = m;
        if(NR < n)
            li = m+1;
        else
            ls = m-1;
    }
    if(af == 0)
        return -1;
    else
        return af;
}
int main()
{
    fin >> n;
    fout << cb(1,ULLONG_MAX-10);
}