#include <fstream>
int zero(int n)
{
    int nr=0;
    while(n>=5)
    {
        nr+=n/5;
        n/=5;
    }
    return nr;
}
int main()
{
    FILE *fin, *fout;
    fin=fopen("fact.in", "r");
    fout=fopen("fact.out", "w");
    long long i=0, pas, p;
    fscanf(fin, "%lld", &p);
    pas=1<<30;
    while(pas!=0)
    {
        if(zero(i+pas)<=p-1)
            i+=pas;
        pas/=2;
    }
    if(zero(i+1)==p)
        fprintf(fout, "%lld", i+1);
    else
        fprintf(fout, "-1");
    return 0;
}