#include<fstream.h>
ifstream f("fact.in");
ofstream g("fact.out");
long p,a=1,z=400000000,e,az;
short ga;
long suma(long x)
{long i,s=0;
for(i=5;i<=x;i*=5)
s+=x/i;
return s;
}
int main()
{
f>>p;
if(p==0)
g<<1;
else
	if(p==1)
		g<<5;
	else
{while(!ga&&a<=z)
	{az=(a+z)/2;
	 e=suma(az);
	 if(e<p)
		a=az+1; 
	 else
		 if(e>p)
			 z=az-1;
		 else
			 ga=1;
	}
if(ga)
	{while(az%5)
		az--;
	g<<az;}
else
	g<<-1;
}
return 0;
}