#include <fstream>
#include <iostream>

using namespace std;
ifstream fin ("fact.in");
ofstream fout("fact.out");
int main()
{
    int n;
    fin >> n;
    if(n == 0) fout << 1;
    else
    {
        for(int i = 5; ; i += 5)
        {
            int sum = 0, x = 5;
            while(x < i)
            {
                sum+=i/x;
                x*=5;
            }
            if(sum == n)
            {
                fout << i;
                break;
            }
        }
    }
    return 0;
}