#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
unsigned int p;
int test_numar(int x)
{
    int nr=0,cinci=5;
    while (x/cinci!=0)
    {
        nr+=x/cinci;
        cinci*=5;
    }
    return nr;
}

unsigned int Cautare_Binara(unsigned int s,unsigned int d)
{
    if (s<=d)
    {
        unsigned int mij=(s+d)/2;
        unsigned int x=test_numar(mij);
        if (x==p) return mij;
        if (x<p) return Cautare_Binara(mij+1,d);
        else return Cautare_Binara(s,mij-1);
    }
}

int main()
{unsigned int x;
    fin>>p;
    //fout<<test_numar(10);
    if (p==0) fout<<"1";
    else {x=Cautare_Binara(1,3000000000);
    while (x%5!=0) x--;
    fout<<x;
    }
    return 0;
}