```cpp
#include <cstdio>
#include <iostream>
#include <vector>
#include <cstring>
#include <algorithm>
#include <queue>
#include <cstdlib>
#include <ctime>
#include <cmath>
#define f(c,a,b) for(int c=a; c<=b; c++)
#define N 2000010
#define pii pair<int,int>
#define mp make_pair
#define fi first
#define se second
#define sl (u<<1)
#define sr ((u<<1)+1)
#define pb push_back
#define eps 1e-8
using namespace std;
typedef double db;
typedef long long ll;
const int mo = 20100403;
ll jc[N]={1};
ll fp(ll a, ll b){ // a^b
ll t = a, ans = 1;
for (int i=0; (1LL<<i)<=b; i++) {
if( (1LL<<i)&b ) ans = ans*t % mo;
t = t*t % mo;
}
return ans;
} //费马小定理
ll my_inv(ll a) { return fp(a,mo-2); }
//扩展欧几里得
ll c(ll n, ll m) { return jc[n]*my_inv(jc[m])%mo*my_inv(jc[n-m])%mo; }
int main(){
// freopen("owo.in","r",stdin);
// ios::sync_with_stdio(false);
// cin.tie(nullptr);
int n,m;
cin>>n>>m;
if(m==1){
cout<<1<<endl;
return 0;
}
f(i,1,N-1) jc[i]=(jc[i-1]*i)%mo;
ll a=c(n+m,n), b=c(n+m,n+1);
// cout<<a<<' '<<b<<endl;
cout<< ( (a-b)%mo+mo )%mo << endl;
return 0;
}
```
by dwbcz @ 2021-05-13 15:12:03
```
ll jc[N]={1};
```
不要在这里初始化，改成
```
ll jc[N];
...
main(){
jc[0]=1;
}
```
by dottle @ 2021-05-13 15:24:30
@[dwbcz](/user/42892)
by dottle @ 2021-05-13 15:25:43
@[dottle](/user/79067) 它过了，蟹蟹~能弱弱的问一句为什么嘛
by dwbcz @ 2021-05-14 14:14:55
考古
by 岂非 @ 2023-06-23 22:53:06
考古
by littlesnake @ 2024-01-18 09:49:57