Problem:
Score : 100 points

Problem Statement

In K-city, there are n streets running east-west, and m streets running north-south. Each street running east-west and each street running north-south cross each other. We will call the smallest area that is surrounded by four streets a block. How many blocks there are in K-city?

Constraints

2 ≤ n, m ≤ 100

Input

Input is given from Standard Input in the following format:

n m

Output

Print the number of blocks in K-city.

Sample Input 1

3 4

Sample Output 1

6

There are six blocks, as shown below:

Sample Input 2

2 2

Sample Output 2

1

There are one block, as shown below:

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <cassert>
#include <cstdio>
#include <cmath>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <queue>
#include <algorithm>

const int MOD = 1000000007, INF = 1111111111;
using namespace std;
using lint = long long;

template <class T>
ostream &operator<<(ostream &os, const vector<T> &vec) {
	for (int i = 0; i < (int)vec.size(); i++) {
		os << vec[i] << (i + 1 == vec.size() ? "" : " ");
	}
	return os;
}

#ifdef _DEBUG
template <class Head>
void dump(const char* str, Head &&h) { cerr << str << " = " << h << "\n"; };
template <class Head, class... Tail>
void dump(const char* str, Head &&h, Tail &&... t) {
	while (*str != ',') cerr << *str++; cerr << " = " << h << "\n";
	dump(str + 1, t...);
}
#define DMP(...) dump(#__VA_ARGS__, __VA_ARGS__)
#else 
#define DMP(...) ((void)0)
#endif

int main() {

	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	int n, m;
	cin >> n >> m;

	cout << (n - 1) * (m - 1) << "\n";

	return 0;
}