Problem: Btoh yuo adn yuor roomatme lhoate wianshg disehs, btu stlil sdmoeboy msut peorrfm tihs cohre dialy. Oen dya yuo decdie to idourtcne smoe syestm. Yuor rmmotaoe sstgegus teh fooniwllg dael. Yuo argee on tow arayrs of ientgres M adn R, nmebur upmicnog dyas (induiclng teh cunrret oen) wtih sicsescuve irnegets (teh ceurrnt dya is zreo), adn yuo wsah teh diehss on dya D if adn olny if terhe etsixs an iednx i scuh taht D mod M[i] = R[i], otwsehrie yuor rmootmae deos it. Yuo lkie teh cncepot, btu yuor rmotaome's cuinnng simle meaks yuo ssecupt sthnoemig, so yuo itennd to vefriy teh fnerisas of teh aemnrgeet.

Yuo aer geivn ayarrs M adn R. Cuaclatle teh pceanregte of dyas on wchih yuo edn up dnoig teh wisahng. Amsuse taht yuo hvae iiiftlneny mnay dyas aehad of yuo. 

Input

The first line of input contains a single integer N (1 ≤ N ≤ 16).

The second and third lines of input contain N integers each, all between 0 and 16, inclusive, and represent arrays M and R, respectively. All M[i] are positive, for each i R[i] < M[i].

Output

Output a single real number. The answer is considered to be correct if its absolute or relative error does not exceed 10 - 4.

Examples

Input

1
2
0


Output

0.500000


Input

2
2 3
1 0


Output

0.666667

Solution (in JAVA):

Solution:
import java.io.*;
import java.math.*;
import java.util.*;

public class B {
	final static int MOD = 1000000007;
	final static int MAX = 720720;
	static int[] M, R;

	public static void main(String[] args) throws Exception {
		FastReader in = new FastReader(System.in);
		int n = in.nextInt();
		M = new int[n];
		R = new int[n];
		for (int i = 0; i < n; i++)
			M[i] = in.nextInt();
		for (int i = 0; i < n; i++)
			R[i] = in.nextInt();
		int me = 0;
		for (int i = 1; i <= MAX; i++) {
			if (me(i))
				me++;
		}
		System.out.println(me / (double)MAX);
	}
	
	public static boolean me(int d) {
		for (int i = 0; i < M.length; i++) {
			if (d % M[i] == R[i])
				return true;
		}
		return false;
	}

	static class FastReader {
	    private boolean finished = false;

	    private InputStream stream;
	    private byte[] buf = new byte[1024];
	    private int curChar;
	    private int numChars;
	    private SpaceCharFilter filter;

	    public FastReader(InputStream stream) {
	        this.stream = stream;
	    }

	    public int read() {
	        if (numChars == -1) {
	            throw new InputMismatchException();
	        }
	        if (curChar >= numChars) {
	            curChar = 0;
	            try {
	                numChars = stream.read(buf);
	            } catch (IOException e) {
	                throw new InputMismatchException();
	            }
	            if (numChars <= 0) {
	                return -1;
	            }
	        }

	        return buf[curChar++];
	    }

	    public int peek() {
	        if (numChars == -1) {
	            return -1;
	        }
	        if (curChar >= numChars) {
	            curChar = 0;
	            try {
	                numChars = stream.read(buf);
	            } catch (IOException e) {
	                return -1;
	            }
	            if (numChars <= 0) {
	                return -1;
	            }
	        }
	        return buf[curChar];
	    }

	    public int nextInt() {
	        int c = read();
	        while (isSpaceChar(c))
	            c = read();
	        int sgn = 1;
	        if (c == '-') {
	            sgn = -1;
	            c = read();
	        }
	        int res = 0;
	        do {
	            if (c == ',') {
	                c = read();
	            }
	            if (c < '0' || c > '9') {
	                throw new InputMismatchException();
	            }
	            res *= 10;
	            res += c - '0';
	            c = read();
	        } while (!isSpaceChar(c));
	        return res * sgn;
	    }

	    public long nextLong() {
	        int c = read();
	        while (isSpaceChar(c))
	            c = read();
	        int sgn = 1;
	        if (c == '-') {
	            sgn = -1;
	            c = read();
	        }
	        long res = 0;
	        do {
	            if (c < '0' || c > '9') {
	                throw new InputMismatchException();
	            }
	            res *= 10;
	            res += c - '0';
	            c = read();
	        } while (!isSpaceChar(c));
	        return res * sgn;
	    }

	    public String nextString() {
	        int c = read();
	        while (isSpaceChar(c))
	            c = read();
	        StringBuilder res = new StringBuilder();
	        do {
	            res.appendCodePoint(c);
	            c = read();
	        } while (!isSpaceChar(c));
	        return res.toString();
	    }

	    public boolean isSpaceChar(int c) {
	        if (filter != null) {
	            return filter.isSpaceChar(c);
	        }
	        return isWhitespace(c);
	    }

	    public static boolean isWhitespace(int c) {
	        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	    }

	    private String readLine0() {
	        StringBuilder buf = new StringBuilder();
	        int c = read();
	        while (c != '\n' && c != -1) {
	            if (c != '\r') {
	                buf.appendCodePoint(c);
	            }
	            c = read();
	        }
	        return buf.toString();
	    }

	    public String nextLine() {
	        String s = readLine0();
	        while (s.trim().length() == 0)
	            s = readLine0();
	        return s;
	    }

	    public String nextLine(boolean ignoreEmptyLines) {
	        if (ignoreEmptyLines) {
	            return nextLine();
	        } else {
	            return readLine0();
	        }
	    }

	    public BigInteger nextBigInteger() {
	        try {
	            return new BigInteger(nextString());
	        } catch (NumberFormatException e) {
	            throw new InputMismatchException();
	        }
	    }

	    public char nextCharacter() {
	        int c = read();
	        while (isSpaceChar(c))
	            c = read();
	        return (char) c;
	    }

	    public double nextDouble() {
	        int c = read();
	        while (isSpaceChar(c))
	            c = read();
	        int sgn = 1;
	        if (c == '-') {
	            sgn = -1;
	            c = read();
	        }
	        double res = 0;
	        while (!isSpaceChar(c) && c != '.') {
	            if (c == 'e' || c == 'E') {
	                return res * Math.pow(10, nextInt());
	            }
	            if (c < '0' || c > '9') {
	                throw new InputMismatchException();
	            }
	            res *= 10;
	            res += c - '0';
	            c = read();
	        }
	        if (c == '.') {
	            c = read();
	            double m = 1;
	            while (!isSpaceChar(c)) {
	                if (c == 'e' || c == 'E') {
	                    return res * Math.pow(10, nextInt());
	                }
	                if (c < '0' || c > '9') {
	                    throw new InputMismatchException();
	                }
	                m /= 10;
	                res += (c - '0') * m;
	                c = read();
	            }
	        }
	        return res * sgn;
	    }

	    public boolean isExhausted() {
	        int value;
	        while (isSpaceChar(value = peek()) && value != -1)
	            read();
	        return value == -1;
	    }

	    public String next() {
	        return nextString();
	    }

	    public SpaceCharFilter getFilter() {
	        return filter;
	    }

	    public void setFilter(SpaceCharFilter filter) {
	        this.filter = filter;
	    }

	    public interface SpaceCharFilter {
	        public boolean isSpaceChar(int ch);
	    }
	}
}