#include <iostream>
#include <algorithm>
#include <fstream>

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



long long nr_0(int n){
long long nr_0uri=0;
int i=5;
while(n/i>0){
nr_0uri+=n/i;
i*=5;

}
return nr_0uri;
}

void bsearch0 (long long st, long long dr, int x) {
    long long m;

    while (st < dr) {
        m = (st + dr) / 2;
        if (nr_0(m) <= x)
            st = m+1;
        else
            dr = m-1;
    }
    m = (st + dr) / 2;

    if (nr_0(m) > x) m --;
    while (nr_0(m-1) == x)m--;
        if(nr_0(m)==x) out<<m;
    else out<< -1;
}



int main()
{in>>n;
bsearch0(1,100000000,n);
   cout<<nr_0(45);

    return 0;
}