bzoj 1856 组合

/**************************************************************
    Problem: 1856
    User: BLADEVIL
    Language: C++
    Result: Accepted
    Time:5220 ms
    Memory:804 kb
****************************************************************/
 
//By BLADEVIL
#include <cstdio>
#define d39 20100403
#define LL long long
 
using namespace std;
 
int n,m;
 
int pw(int x,int p) {
    int ans=1;
    while (p) {
        if (p&1) ans=((LL)ans*x)%d39;
        x=((LL)x*x)%d39;
        p>>=1;
    }
    return ans;
}
 
int c(int n,int m) {
    int ans=1;
    for (int i=m+1;i<=n;i++) ans=((LL)ans*i)%d39;
    for (int i=1;i<=n-m;i++) ans=((LL)ans*pw(i,d39-2))%d39; 
    return ans;
}
 
int main() {
    scanf("%d%d",&n,&m);
    printf("%d\n",(c(n+m,n)-c(n+m,n+1)+d39)%d39);
    return 0;
}