#include <fstream>
#define NMAX 50000000

using namespace std;
unsigned char A[NMAX];
long long P;

fstream fout("fact.out",ios::out);
void preproc()
{
	memset(A,1,sizeof(A));
	int i,j;
	for(j=5;j<NMAX/5;j*=5)
		for(i=j;i<NMAX;i+=j)
		{
			A[i]++;
		}
	
}

void proc()
{
	
	
	long long S=0;
	int i=0;
	while(P>S)
	{
		S=S+A[++i];
	}
	if(P!=0)
		if(P==S)
			fout<<i*5;
		else fout<<"-1";
	else fout<<"1";
	fout<<"\n";
}

int main(int argc,char *agv[])
{
	fstream fin("fact.in",ios::in);
	preproc();
	fin>>P;
	proc();
	fin.close();
}