#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
    unsigned p,nr;
    fin >> p;
    long long int a=0,b=100000005,c,i;
    if(p==0)
        fout << 1 << "\n";
    else
    while(a!=b)
    {
        nr=0;
        c=(a+b)/2;
        for(i=5;i<=c;i*=5)
            nr+=c/i;
        if(nr==p)
            {while(c%5!=0)
                c--;
            fout << c;break;}
        if(nr<p)
            a=c+1;
        if(nr>p)
            b=c-1;
    }
    return 0;
}