全都是m+n-1，下图都写成m-n-1了，没有脑子o(╥﹏╥)o

 题目链接：214. Devu和鲜花 - AcWing题库

#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int mod = 1e9+7;
ll A[25];
ll Pow(ll a, ll k){
    ll ans = 1;
    while(k){
        if(k & 1) ans = ans*a%mod;
        a = a*a%mod;
        k>>=1;
    }
    return ans;
}
ll down = 1;
ll C(ll a, ll b) {
    if(a<b) return 0;
    ll up = 1;
    for (ll i = a; i>=(a-b+1); i--) up = i%mod *up %mod;
    return up * Pow(down, mod-2)%mod;
}
int main(){
    int n; scanf("%d", &n);
    ll m; scanf("%lld", &m);
    for(int i=0; i<n; i++) scanf("%lld", &A[i]);
    for(ll j = 1; j <= n-1; j++) down = j*down%mod;
    ll res = 0;
    for(int i=0; i< 1<<n; i++) { //2^n, 用二进制来表示这一对组合
        ll a = m + n - 1, b = n - 1;
        int sign = 1;
        for(int j = 0; j < n; j++) //代表n个东西
            if(i >> j & 1) { //i的这一位是1, 则选
                sign *= -1;  //容斥,奇正偶负
                a -= A[j]+1;
            }
        res = ((res + C(a, b) * sign)%mod + mod)%mod;
    }
    cout << (res + mod)%mod;
    return 0;
}