#include <fstream>


using namespace std;

int main()
{
    ifstream in ("fact.in");
    ofstream out ("fact.out");
    int n=1, p, ci;
    in >> p;
    int p2=0, p5=0;
    for(int i=1; i<=n; ++i) {
        ci=i;
        while(ci%2==0) {
            p2++;
            ci/=2;
        }
        while(ci%5==0) {
            p5++;
            ci/=5;
        }
        int x=min(p2,p5);
        if(x==p) out << n;
            else
                n++;
        if(x>p)
            break;
    }
    in.close();
    out.close();
    return 0;
}