#include<fstream>
using namespace std;
ifstream F("fact.in");
ofstream G("fact.out");
int p,i,j,t,s,k,l;
int main()
{
	F>>p;
	for(s=1<<27;s;s>>=1)
        if(s+i<=100000000) {
            for(j=5*(i+s),t=0,k=5;k<=j;k*=5)
                t=t+j/k;
            if(t<=p)
                i+=s,l=t;
        }
    G<<(!p?1:(l==p?5*i:-1));
    return 0;
}