#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
long long nrzero(long long n)
{
    long long put5=5,cnt=0;
    while(n/put5)
    {
        cnt+=n/put5;
        put5*=5;
    }
    return cnt;
}
long long cautbin(int n)
{
    long long pos=0,step=1LL*1<<60;
    for(;step>0;step/=2)
        if(step+pos<1LL*1<<60&&nrzero(step+pos)<n)
            pos+=step;
    if(nrzero(pos+1)==n)
        return pos+1;
    else return -1;
}
int main()
{
    int n;
    in>>n;
    out<<cautbin(n);
    return 0;
}