#![allow(unused_macros)]
#![allow(dead_code)]
#![allow(unused_imports)]

use itertools::Itertools;
use text_io::*;

fn main() {
    const U_INF: usize = 1 << 60;
    const I_INF: isize = 1 << 60;
    const MOD: i128 = 1000000007;

    let n: usize = read!();
    let k: usize = read!();
    let mut a = Vec::new();
    for _ in 0..n {
        let ai: usize = read!();
        a.push(ai);
    }

    let mut dp = vec![vec![0; k + 10]; n + 10];
    for j in 0..=k {
        dp[0][j] = 1;
    }
    for i in 1..=n {
        for j in 0..=k {
            // dp[i-1]は累積和になっていると想定する
            let right = dp[i - 1][j];
            let left = if j < (a[i - 1] + 1) {
                0
            } else {
                dp[i - 1][j - a[i - 1] - 1]
            };
            dp[i][j] = right - left;
        }

        if i != n {
            for j in 1..=k {
                dp[i][j] += dp[i][j - 1];
                dp[i][j] %= MOD;
            }
        }
    }

    println!("{}", dp[n][k]);

    // let mut dp = vec![vec![0; k * 3 + 10]; n + 10];
    // dp[0][0] = 1;
    // for i in 0..n {
    //     for j in 0..=k {
    //         let dij = dp[i][j];
    //         let ai = a[i];
    //         dp[i + 1][j] += dij;
    //         dp[i + 1][j] %= MOD;
    //         dp[i + 1][j + ai + 1] -= dij;
    //         dp[i + 1][j + ai + 1] %= MOD;
    //     }
    //
    //     for j in 0..k {
    //         dp[i + 1][j + 1] += dp[i + 1][j];
    //         dp[i + 1][j + 1] %= MOD;
    //     }
    // }
    // println!("{}", dp[n][k]);
}
