#include<fstream>
using namespace std; ifstream in("fact.in"); ofstream out("fact.out");

int p,n;

int zero(int n){
	int r=0;
	while (n >= 5)
		r += (n /= 5);
	return r;
}
int search(int x){
	int i,pos=1<<30;
	for ( i = 0 ; pos ; pos>>=1)
		if (zero(i+pos)<p)
			i+=pos;
	return i+1;
}
/*bool verific(int x,int y){
	return x==y;
}*/
int main(){
	int i;
	in>>p;
	if (zero(search(p)) == p)
		out<<search(p);
	else
		out<<"-1";
}