#include <fstream>
using namespace std;

inline int count_zero(int x)
{
    int n=0;
    while (x) {
        n+=x/5;
        x/=5;
    }
    return n;
}

int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");

    int k, li, ls, mij;
    fin>>k;
    if (!k){ fout<<1; return 0; }

    li=1, ls=k*5;
    while (li<=ls) {
        mij=(li+ls)>>1;
        count_zero(mij)<k ? li=mij+1 : ls=mij-1;
    }

    fout<<(count_zero(li)==k ? li : -1);
    return 0;
}