#include<fstream.h>
ifstream in("fact.in");
ofstream out("fact.out");

long int i,n2,n5,n;

void divi()
{
int c;
c=i;
while(!(c%2))
	{n2++;c/=2;}
while(!(c%5))
	{n5++;c/=5;}
}


int main()
{
in>>n;
while(n2<n || n5<n)
	{
	i++;
	divi();
	}
out<<i;
return 0;
}