#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int p(int a)
{
    int putere=0;
    while(a%5==0)
    {
        putere++;
        a/=5;
    }
    return putere;
}
int main()
{
    int n;
    fin>>n;
    if(n==0) fout<<1;
    else {
        int pow5=0,r=0;
        while(n>pow5)
        {
            r+=5;
            pow5+=p(r);
        }
        if(n<pow5) fout<<-1;
        else fout<<r;
    }
    return 0;
}