#include "stdio.h"
int p;int long c,egalitate=0;

int zero(long int z)
{
int nr=0;
	
	while(z)
		{
		nr=nr+z/5;
		z/=5;	
		}
	return nr;
	
}




int cautare(long int a,long int b)
{
int z,y=-1;

while (a<=b)
{
	


c=a+(b-a)/2;

z=zero(c);


if(z>=p)
	{
		
	if(z==p)
			y=c;
	b=c-1;
	
	} else a=c+1;
}
			
return 	y;	
	
	
}

int main()
{
	

long int a=0;
long int b;
long int n;


FILE *f,*g;


f=fopen("fact.in","r");
g=fopen("fact.out","w");
fscanf(f,"%d",&p);
b=p*5;

	
if (p==0) n=1; else n=cautare(a,b);	
	


fprintf(g,"%ld",n);



fclose(g);
}