#include <fstream>

using namespace std;

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

int main()
{
    int p,n,pp=0,cp;
    in>>p;
    n=p*5;
    cp=n;
    while(cp>24)
    {
        cp/=25;
        pp++;
    }
    n=n-pp*5;
    if(p==0) n++;
    out<<n;
    return 0;
}