#include <fstream>

using namespace std;
ifstream in ("fact.in");
ofstream out ("fact.out");

int main()
{
    int n,r,i=5,z=1;
    bool ok=1;
    in>>n;
    r=n*5;
    if(r==0)
    {
        ok=0;
        r=1;
    }
    while(ok)
    {
        if(r>i*5)
            r-=5*z;
        else
            ok=0;
        i*=5;
        z++;
    }
    out<<r;
    return 0;
}