Rudolf is on his way to the castle. Before getting into the castle, the security staff asked him a question:

Given two binary numbers a and b of length n. How many different ways of swapping two digits in a (only in a, not b) so that bitwise OR of these two numbers will be changed? In other words, let c be the bitwise OR of a and b, you need to find the number of ways of swapping two bits in a so that bitwise OR will not be equal to c.

Note that binary numbers can contain leading zeros so that length of each number is exactly n.

[Bitwise OR](https://en.wikipedia.org/wiki/Bitwise_operation#OR) is a binary operation. A result is a binary number which contains a one in each digit if there is a one in at least one of the two numbers. For example, 01010_2 OR 10011_2 = 11011_2.

Well, to your surprise, you are not Rudolf, and you don't need to help him… You are the security staff! Please find the number of ways of swapping two bits in a so that bitwise OR will be changed.

Input

The first line contains one integer n (2≤ n≤ 10^5) — the number of bits in each number.

The second line contains a binary number a of length n.

The third line contains a binary number b of length n.

Output

Print the number of ways to swap two bits in a so that bitwise OR will be changed.

Examples

Input

5
01011
11001


Output

4


Input

6
011000
010011


Output

6

Note

In the first sample, you can swap bits that have indexes (1, 4), (2, 3), (3, 4), and (3, 5).

In the second example, you can swap bits that have indexes (1, 2), (1, 3), (2, 4), (3, 4), (3, 5), and (3, 6).
/*
 * Author: Minho Kim (ISKU)
 * Date: August 8, 2018
 * E-mail: minho.kim093@gmail.com
 *
 * https://github.com/ISKU/Algorithm
 * http://codeforces.com/problemset/problem/1017/B
 */

import java.io.*;

public class B {

	private static void solve() {
		int N = io.nextInt();
		char[] A = io.nextToCharArray();
		char[] B = io.nextToCharArray();

		int one = 0;
		int zeroone = 0;
		for (int i = 0; i < N; i++) {
			if (A[i] == '1')
				one++;
			if (A[i] == '0' && B[i] == '1')
				zeroone++;
		}

		long answer = 0;
		for (int i = 0; i < N; i++) {
			if (A[i] == '0' && B[i] == '0')
				answer += one;
			if (A[i] == '1' && B[i] == '0')
				answer += zeroone;
		}

		io.print(answer);
	}

	private static FastIO io;

	public static void main(String... args) {
		io = new FastIO(System.in, System.out);
		solve();
		io.close();
	}

	/**
	 * https://github.com/ISKU/FastIO-Java
	 * 
	 * @author Minho Kim <minho.kim093@gmail.com>
	 */
	private static class FastIO {

		public static final int DEFAULT_BUFFER_SIZE = 65536;
		public static final int DEFAULT_INTEGER_SIZE = 10;
		public static final int DEFAULT_LONG_SIZE = 19;
		public static final int DEFAULT_WORD_SIZE = 256;
		public static final int DEFAULT_LINE_SIZE = 100001;
		public static final int EOF = -1;

		private final InputStream in;
		private final OutputStream out;

		private byte[] inBuffer;
		private int nextIn, inLength;
		private byte[] outBuffer;
		private int nextOut;

		private char[] charBuffer;
		private byte[] byteBuffer;

		public FastIO(InputStream in, OutputStream out, int inBufferSize, int outBufferSize) {
			this.in = in;
			this.inBuffer = new byte[inBufferSize];
			this.nextIn = 0;
			this.inLength = 0;

			this.out = out;
			this.outBuffer = new byte[outBufferSize];
			this.nextOut = 0;

			this.charBuffer = new char[DEFAULT_LINE_SIZE];
			this.byteBuffer = new byte[DEFAULT_LONG_SIZE];
		}

		public FastIO(InputStream in, OutputStream out) {
			this(in, out, DEFAULT_BUFFER_SIZE, DEFAULT_BUFFER_SIZE);
		}

		public FastIO(InputStream in, OutputStream out, int bufferSize) {
			this(in, out, bufferSize, bufferSize);
		}

		public char nextChar() {
			byte b;
			while (isSpace(b = read()))
				;

			return (char) b;
		}

		public String next() {
			byte b;
			while (isSpace(b = read()))
				;

			int pos = 0;
			do {
				charBuffer[pos++] = (char) b;
			} while (!isSpace(b = read()));

			return new String(charBuffer, 0, pos);
		}

		public String nextLine() {
			byte b;
			int pos = 0;

			while (!isLine(b = read()))
				charBuffer[pos++] = (char) b;

			return new String(charBuffer, 0, pos);
		}

		public int nextInt() {
			byte b;
			while (isSpace(b = read()))
				;

			boolean negative = false;
			int result = b - '0';
			if (b == '-') {
				negative = true;
				result = 0;
			}

			while (isDigit(b = read()))
				result = (result * 10) + (b - '0');

			return negative ? -result : result;
		}

		public long nextLong() {
			byte b;
			while (isSpace(b = read()))
				;

			boolean negative = false;
			long result = b - '0';
			if (b == '-') {
				negative = true;
				result = 0;
			}

			while (isDigit(b = read()))
				result = (result * 10) + (b - '0');

			return negative ? -result : result;
		}

		public float nextFloat() {
			byte b;
			while (isSpace(b = read()))
				;

			int pos = 0;
			do {
				charBuffer[pos++] = (char) b;
			} while (!isSpace(b = read()));

			return Float.parseFloat(new String(charBuffer, 0, pos));
		}

		public float nextFloat2() {
			byte b;
			while (isSpace(b = read()))
				;

			boolean negative = false;
			float result = b - '0';
			if (b == '-') {
				negative = true;
				result = 0;
			}

			while (isDigit(b = read()))
				result = (result * 10) + (b - '0');

			float d = 1;
			if (b == '.') {
				while (isDigit(b = read()))
					result += (b - '0') / (d *= 10);
			}

			return negative ? -result : result;
		}

		public double nextDouble() {
			byte b;
			while (isSpace(b = read()))
				;

			int pos = 0;
			do {
				charBuffer[pos++] = (char) b;
			} while (!isSpace(b = read()));

			return Double.parseDouble(new String(charBuffer, 0, pos));
		}

		public double nextDouble2() {
			byte b;
			while (isSpace(b = read()))
				;

			boolean negative = false;
			double result = b - '0';
			if (b == '-') {
				negative = true;
				result = 0;
			}

			while (isDigit(b = read()))
				result = (result * 10) + (b - '0');

			double d = 1;
			if (b == '.') {
				while (isDigit(b = read()))
					result += (b - '0') / (d *= 10);
			}

			return negative ? -result : result;
		}

		public char[] nextToCharArray() {
			byte b;
			while (isSpace(b = read()))
				;

			int pos = 0;
			do {
				charBuffer[pos++] = (char) b;
			} while (!isSpace(b = read()));

			char[] array = new char[pos];
			System.arraycopy(charBuffer, 0, array, 0, pos);
			return array;
		}

		public int[] nextIntArray(int size) {
			int[] array = new int[size];
			for (int i = 0; i < size; i++)
				array[i] = nextInt();

			return array;
		}

		public long[] nextLongArray(int size) {
			long[] array = new long[size];
			for (int i = 0; i < size; i++)
				array[i] = nextLong();

			return array;
		}

		public int[][] nextInt2DArray(int Y, int X) {
			int[][] array = new int[Y][X];
			for (int y = 0; y < Y; y++)
				for (int x = 0; x < X; x++)
					array[y][x] = nextInt();

			return array;
		}

		public void print(char c) {
			write((byte) c);
		}

		public void print(String s) {
			for (int i = 0; i < s.length(); i++)
				write((byte) s.charAt(i));
		}

		public void print(int i) {
			if (i == 0) {
				write((byte) '0');
				return;
			}
			if (i == Integer.MIN_VALUE) {
				write((byte) '-');
				write((byte) '2');
				write((byte) '1');
				write((byte) '4');
				write((byte) '7');
				write((byte) '4');
				write((byte) '8');
				write((byte) '3');
				write((byte) '6');
				write((byte) '4');
				write((byte) '8');
				return;
			}

			if (i < 0) {
				write((byte) '-');
				i = -i;
			}

			int pos = 0;
			while (i > 0) {
				byteBuffer[pos++] = (byte) ((i % 10) + '0');
				i /= 10;
			}

			while (pos-- > 0)
				write(byteBuffer[pos]);
		}

		public void print(long l) {
			if (l == 0) {
				write((byte) '0');
				return;
			}
			if (l == Long.MIN_VALUE) {
				write((byte) '-');
				write((byte) '9');
				write((byte) '2');
				write((byte) '2');
				write((byte) '3');
				write((byte) '3');
				write((byte) '7');
				write((byte) '2');
				write((byte) '0');
				write((byte) '3');
				write((byte) '6');
				write((byte) '8');
				write((byte) '5');
				write((byte) '4');
				write((byte) '7');
				write((byte) '7');
				write((byte) '5');
				write((byte) '8');
				write((byte) '0');
				write((byte) '8');
				return;
			}

			if (l < 0) {
				write((byte) '-');
				l = -l;
			}

			int pos = 0;
			while (l > 0) {
				byteBuffer[pos++] = (byte) ((l % 10) + '0');
				l /= 10;
			}

			while (pos-- > 0)
				write(byteBuffer[pos]);
		}

		public void print(float f) {
			String sf = Float.toString(f);
			for (int i = 0; i < sf.length(); i++)
				write((byte) sf.charAt(i));
		}

		public void print(double d) {
			String sd = Double.toString(d);
			for (int i = 0; i < sd.length(); i++)
				write((byte) sd.charAt(i));
		}

		public void printls(char c) {
			print(c);
			write((byte) ' ');
		}

		public void printls(String s) {
			print(s);
			write((byte) ' ');
		}

		public void printls(int i) {
			print(i);
			write((byte) ' ');
		}

		public void printls(long l) {
			print(l);
			write((byte) ' ');
		}

		public void printls(float f) {
			print(f);
			write((byte) ' ');
		}

		public void printls(double d) {
			print(d);
			write((byte) ' ');
		}

		public void println(char c) {
			print(c);
			write((byte) '\n');
		}

		public void println(String s) {
			print(s);
			write((byte) '\n');
		}

		public void println(int i) {
			print(i);
			write((byte) '\n');
		}

		public void println(long l) {
			print(l);
			write((byte) '\n');
		}

		public void println(float f) {
			print(f);
			write((byte) '\n');
		}

		public void println(double d) {
			print(d);
			write((byte) '\n');
		}

		public void printf(String format, Object... args) {
			String s = String.format(format, args);
			for (int i = 0; i < s.length(); i++)
				write((byte) s.charAt(i));
		}

		public void fprint(char c) {
			print(c);
			flushBuffer();
		}

		public void fprint(String s) {
			print(s);
			flushBuffer();
		}

		public void fprint(int i) {
			print(i);
			flushBuffer();
		}

		public void fprint(long l) {
			print(l);
			flushBuffer();
		}

		public void fprint(float f) {
			print(f);
			flushBuffer();
		}

		public void fprint(double d) {
			print(d);
			flushBuffer();
		}

		public void fprintf(String format, Object... args) {
			printf(format, args);
			flushBuffer();
		}

		private byte read() {
			if (nextIn >= inLength) {
				if ((inLength = fill()) == EOF)
					return EOF;
				nextIn = 0;
			}

			return inBuffer[nextIn++];
		}

		private void write(byte b) {
			if (nextOut >= outBuffer.length)
				flushBuffer();

			outBuffer[nextOut++] = b;
		}

		private int fill() {
			try {
				return in.read(inBuffer, 0, inBuffer.length);
			} catch (Exception e) {
				throw new RuntimeException(e);
			}
		}

		public void flush() {
			if (nextOut == 0)
				return;

			flushBuffer();
		}

		private void flushBuffer() {
			try {
				out.write(outBuffer, 0, nextOut);
			} catch (Exception e) {
				throw new RuntimeException(e);
			}

			nextOut = 0;
		}

		public void close() {
			flush();
		}

		private boolean isDigit(byte b) {
			return b >= '0' && b <= '9';
		}

		private boolean isLine(byte b) {
			return b == '\n' || b == '\r' || b == EOF;
		}

		private boolean isSpace(byte b) {
			return b == ' ' || b == '\t' || b == '\n' || b == '\r' || b == '\f' || b == EOF;
		}
	}
}