#include <fstream>

using namespace std;

int P;

int zero (int n)
{
    int r=0;
    while(n>=5)
    {
        r+=n/5;
        n/=5;
    }
    return r;
}

int cauta (int p)
{
    int i, pas=1<<30;
    for(i=0; pas!=0; pas/=2)
        if(zero(i+pas)<P)
            i+=pas;
    return i+1;
}

int main()
{
    ifstream in("fact.in");
    ofstream out("fact.out");
    int N;
    in>>P;
    N=cauta(P);
    if(zero(N)==P)
        out<<N;
    else out<<"-1";

    return 0;
}