#include <fstream>

using namespace std;
ifstream cin("fact.in");
ofstream cout("fact.out");
int n;
int main()
{
    cin>>n;
    if(n==0)
    {
        cout<<"1";
        return 0;
    }
    long long int i=1;
    while(n>0)
    {
        long long int c=i;
        while(c%5==0)
        {
            c=c/5;
            n--;
        }
        i++;
    }
    cout<<i-1;
    return 0;
}