bzoj1485: [HNOI2009]有趣的数列

/*************************************************************
Problem: bzoj 1485 [HNOI2009]有趣的数列
User: fengyuan
Language: C++
Result: Accepted
Time: 720 ms
Memory: 18476 kb
Submit_Time: 2017-12-15 11:23:35
*************************************************************/

#include<bits/stdc++.h>
#define rep(i, x, y) for (int i = (x); i <= (y); i ++)
#define down(i, x, y) for (int i = (x); i >= (y); i --)
#define mid ((l+r)/2)
#define lc (o<<1)
#define rc (o<<1|1)
#define pb push_back
#define mp make_pair
#define PII pair<int, int>
#define F first
#define S second
#define B begin()
#define E end()
using namespace std;
typedef long long LL;
//head

const int N = 2000010;
int n, MOD, cnt;
int p[N/10], a[N/10], vis
, id
;

inline void makePrime(int limit)
{
rep(i, 2, limit){
if (!vis[i]) p[++ cnt] = i, vis[i] = i, id[i] = cnt;
for (int j = 1; j <= cnt && i*p[j] <= limit; j ++){
vis[i*p[j]] = p[j];
id[i*p[j]] = j;
if (i%p[j] == 0) break;
}
}
}

inline void cal(int x, int v)
{
while (x != 1){
a[id[x]] += v;
x /= vis[x];
}
}

inline int ksm(int x, int P)
{
int ret = 1;
while (P){
if (P&1) ret = 1LL*ret*x%MOD;
x = 1LL*x*x%MOD; P >>= 1;
} return ret;
}

int main()
{
scanf("%d%d", &n, &MOD);
makePrime(2*n);
//C(2n,n)/(n+1)
//n+2~2n +1
rep(i, n+2, 2*n) cal(i, 1);
//1~n -1
rep(i, 1, n) cal(i, -1);
int ans = 1;
rep(i, 1, cnt) ans = 1LL*ans*ksm(p[i], a[i])%MOD;
printf("%d\n", ans);
return 0;
}