public class Euler255 {

	static double totalcounts = 0;
	public static void main(String[] args) {
		long a = (long) Math.pow(10, 13); 
		long b = (long) Math.pow(10, 14)-1; 
		a = (long) Math.pow(10, 13); 
		b = (long) Math.pow(10, 14)-1; 
		long xzero = xzero((long) a);
		long time = System.currentTimeMillis();
		count(a,b,1,xzero);
		System.out.println(totalcounts/(b-a+1));
		System.out.println("Total Time :" + (System.currentTimeMillis()-time) + "ms");
	}
	
	public static long numberOfIteration(long n) {
		long xk = xzero(n);
		long nextxk = nextxk(n, xk); 
		int count = 1;
		while(xk!=nextxk) {
			xk = nextxk;
			nextxk = nextxk(n,xk);
			count++;
		}
		return count;
	}

	public static long xzero(long n) {
		long d = numberOfDigits(n);
		if (d%2 == 0) {
			return (long) (7*Math.pow(10, (d-2)/2));
		}
		else {
			return (long) (2*Math.pow(10, (d-1)/2));
		}
	}

	public static long numberOfDigits(long n) {
		long count=1;
		while (n/10>0) {
			count++;
			n=n/10;
		}
		return count;
	}

	public static long nextxk(long n, long xk) {
		double n1 = n;
		double toto = n1/xk;
		double tutu = Math.ceil(toto);
		double trtr = tutu + xk;
		double tata = trtr/2;
		double tktk = Math.floor(tata);
		long result = (long) tktk;
		return result;
	}

	public static void count(long a,long b,int iter, long xk) {
		long nexta = nextMultiple(a, xk);
		long nextxk = nextxk(a,xk);

		while (nexta<b) {
			if (xk == nextxk) {
				totalcounts+=iter*(nexta-a+1);
			} else {
				count(a,nexta,iter+1,nextxk);
			}
			a=nexta+1;
			nexta= nexta+xk;
			nextxk=nextxk(a,xk);
		}
		
		if (xk == nextxk) {
			totalcounts+=iter*(b-a+1);
		} else {
			count(a,b,iter+1,nextxk);
		}
	
		
	}

	public static long nextMultiple(long a, long multiple) {
		return (((a-1)/multiple)+1)*multiple;
	}
}