#include<bits/stdc++.h>
#define LL long long
using namespace std;
const int N = 1e3 + 5;
int n,m;
int dp[N][N],a[N];
template <typename T> inline void read(T &x){
	x = 0;int t = 1;char c = getchar();
	for(;!isdigit(c);c = getchar()){
		if(c == '-'){
			t = -1;
		}
	}
	for(;isdigit(c);c = getchar()){
		x = (x << 1) + (x << 3) + (c ^ 48);
	}
	x = t * x;
} 
template <typename T> void print(T x){
	if (x < 0){
		x *= -1;
		putchar('-');
	}
	if(x > 9){
		print(x / 10);
	}
	putchar(x % 10 + 48);
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(nullptr);
	read(n);
	read(m);
	//cout << n << m;
	for(int i = 1;i <= n;i++){
		read(a[i]);
	}
	for(int i = 0 ;i <= m;i++){
		dp[0][i] = 1;
	}

	for(int i = 1;i <= n;i++){
		for(int j = 1;j <= m;j++){
			for(int k = 0;k <= j && k <= a[j] && k <= i;k++){
				dp[i][j] = (dp[i - k][j - 1] + dp[i][j]);
			}
		}
	}
	print(dp[n][m]  % 1000007);
	return 0;
}