Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<cstring>

using namespace std;

int n,m;

#define MAXN 1000001

int prime[MAXN],tot = 0;

int pr[MAXN];

bool isprime[MAXN];

int mindiv[MAXN];

int cnt[MAXN];

struct bigint

{

	int a[100];

	int l;

	bigint(){l = 1;a[1] = 1;}

	friend bigint operator * (bigint x,int y)

	{

		for(int i = 1;i <= x.l;++i)

		{

			x.a[i] *= y;

		}

		for(int i = 1;i <= x.l;++i)

		{

			x.a[i + 1] += x.a[i] / 10;

			x.a[i] %= 10;

		}

		while(x.a[x.l + 1] > 0)

		{

			++x.l;

			x.a[x.l + 1] += x.a[x.l] / 10;

			x.a[x.l] %= 10;

		}

		if(x.l > 50)

		{

			for(int i = 50 + 1;i <= x.l;++i)x.a[i] = 0;

			x.l = 50;

		}

		while(x.a[x.l] == 0)--x.l;

		return x;

	}

}t;

void pt(bigint k)

{

	for(int i = k.l;i >= 1;--i)

	{

		printf("%d",k.a[i]);

	}

	return;

}

int main()

{

	scanf("%d%d",&n,&m);

	if(n < m)swap(n,m);

	for(int i = 2;i <= n;++i)isprime[i] = true;

	for(int i = 2;i <= n;++i)

	{

		if(isprime[i])

		{

			prime[++tot] = i;

			mindiv[i] = i;

			pr[i] = tot;

		}

		for(int j = 1;j <= tot && i * prime[j] <= n;++j)

		{

			isprime[i * prime[j]] = false;

			mindiv[i * prime[j]] = prime[j];

			if(i % prime[j] == 0)break;

		}

	}

	for(int i = 1;i <= n;++i)

	{

		int k = i;

		while(k != 1)

		{

			++cnt[pr[mindiv[k]]];

			k /= mindiv[k];

		}

	}

	for(int i = 1;i <= m;++i)

	{

		int k = i;

		while(k != 1)

		{

			--cnt[pr[mindiv[k]]];

			k /= mindiv[k];

		}

	}

	for(int i = 1;i <= n - m;++i)

	{

		int k = i;

		while(k != 1)

		{

			--cnt[pr[mindiv[k]]];

			k /= mindiv[k];

		}

	}

	for(int i = 1;i <= tot;++i)

	{

		for(int j = 1;j <= cnt[i];++j)

		{

			t = t * prime[i];

		}

	}

	pt(t);

	return 0;

}