#include <fstream>

using namespace std;

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

int p, n;

int f(int n)
{
    int t=5, ret=0;
    while(t<=n)
    {
        ret=ret+n/t;
        t*=5;
    }
    return ret;
}
int cautbin(int left, int right)
{
    if(left>right)
        return -1;
    int m=(left + right)/2;

    if(f(m)>p)  cautbin (left, m-1);
    else if (f(m)<p)    cautbin(m+1, right);
    else
    {
        while(m%5!=0)   m--;
        return m;
    }
}

int main()
{
    fin>>p;
    if(p==0)    fout << 1;
    else fout<<cautbin(1, 2000000000);
    return 0;
}