#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int main()
{
    long long p,c=0,i,i1;
    int n,ok=1;
    in>>p;
    i=5; c=0;
    while(c<=p&&ok==1)
    {
       if(c==p)
            {n=i;ok=0;}
        else
       {i1=i;
        while(i1>0&&i1%5==0)
        {
            c++;
            i1=i1/5;
        }
        i=i+5;}
    }
    out<<i-5;
    return 0;
}