#include<stdio.h>
int a=0,c=0,d=0,n=0,e=0,f;
FILE*j;
FILE*g;
int main()
{
j=fopen("fact.in","r");
fscanf(j,"%d",&f);
while(a<f)
	{
		++a;
		++c;
		n=n+5;
		d=n;
		if(c%5==0)
		{
			while(d%5==0)
			{
				++e;
				d=d/5;
			}
			if(e>1) a=a+e-1;
			e=0;
		}
	}
if(a>f) n=-1;
if(f==0) n=1;
fclose(j);
g=fopen("fact.out","w");
fprintf(g,"%d",n);
fclose(g);
}