Problem:
﻿Score: 100 points

Problem Statement

There is a farm whose length and width are A yard and B yard, respectively. A farmer, John, made a vertical road and a horizontal road inside the farm from one border to another, as shown below: (The gray part represents the roads.)

What is the area of this yard excluding the roads? Find it.

Note

It can be proved that the positions of the roads do not affect the area.

Constraints

A is an integer between 2 and 100 (inclusive).

B is an integer between 2 and 100 (inclusive).

Input

Input is given from Standard Input in the following format:

A B

Output

Print the area of this yard excluding the roads (in square yards).

Sample Input 1

2 2

Sample Output 1

1

In this case, the area is 1 square yard.

Sample Input 2

5 7

Sample Output 2

24

In this case, the area is 24 square yards.

Solution in C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;

public static partial class Program
{
    //テンプレここから
    public static int ToInt(this string str)
    {
        return int.Parse(str);
    }

    public static long ToLong(this string str)
    {
        return long.Parse(str);
    }
    public static IEnumerable<int> ToInt(this string[] strs)
    {
        return strs.Select(x => x.ToInt());
    }

    public static IEnumerable<long> ToLong(this string[] strs)
    {
        return strs.Select(x => x.ToLong());
    }
    public static IEnumerable<int> SplToInt(this string str, char opr = ' ')
    {
        return str.Split(opr).ToInt();
    }

    public static IEnumerable<long> SplToLong(this string str, char opr = ' ')
    {
        return str.Split(opr).ToLong();
    }
    public static string CRL()
    {
        return Console.ReadLine();
    }
    public static void CWL(object obj)
    {
        Console.WriteLine(obj);
    }
    public static int Diff(int a, int b)
    {
        return Math.Abs(Math.Max(a, b) - Math.Min(a, b));
    }
    public static long Diff(long a, long b)
    {
        return Math.Abs(Math.Max(a, b) - Math.Min(a, b));
    }
    public static int Sign(this int i)
    {
        return Math.Sign(i);
    }
    //テンプレここまで
}

public static partial class Program
{
    static void Main()
    {
        var str = CRL();
        var k = CRL().ToLong();
        var len = Math.Min(str.Length, k);
        for (int i = 0; i < len; i++)
        {
            if (str[i] != '1')
            {
                CWL(str[i]);
                return;
            }
        }

        CWL(1);
    }
}