#include<iostream.h>
#include<fstream.h>
main()
{
int a,i,n;
long p;
i=1;
n=1;
a=1;
ifstream f("fact.in");
f>>p;
f.close();
while(i<=p)
	{
	n++;
	a=a*n;
	while(a>=10)
		{
		i++;
		a=a/10;
		}

	}
ofstream g("fact.out");
g<<n;
g.close();
}