#include <fstream>
using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int getzero(const int& x)
{
    int y = 5, cnt = 0;
    while (y <= x)
    {
        cnt = cnt + x / y;
        y *= 5;
    }
    return cnt;
}

int binary(int left, int right, const int& p)
{
    if (left > right) return -1;
    else
    {
        int mij = (right-left) / 2 + left;
        int n = getzero(mij);
        if (n == p) return mij;
        else if (n > p) return binary(left, mij-1, p);
        else return binary(mij+1, right, p);
    }
}

int main()
{
    int P; in >> P;
    int n;
    if (P == 0) { out << 1; return 0; }
    n = binary(1, int(2e9), P);
    if (n > 0) while (n % 5 != 0) --n;
    out << n;

    return 0;
}