#include <iostream>
#include <fstream>
using namespace std;
int zero (int n)
{
    int rez;
    rez=0;
    while(n>=5)
    {
        rez+=n/5;
        n/=5;
    }
    return rez;
}
int main()
{
    int n, p, min, i;
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    f.close();
    min=5;
    while(zero(min)!=p)
        min+=5;
    g<<min;
    return 0;
}