use std::error::Error;
use std::io;

fn main() {
    if let Err(e) = run() {
        panic!("failed.");
    }
}

fn run() -> Result<(), Box<Error>> {
    let mut buffer = String::new();
    io::stdin().read_line(&mut buffer)?;
    let first_line: Vec<usize> = buffer.split_whitespace()
        .map(|x| x.parse::<usize>().unwrap())
        .collect();
    let n = first_line[0];
    let k = first_line[1];

    buffer.clear();
    io::stdin().read_line(&mut buffer)?;
    let candies: Vec<i32> = buffer.split_whitespace()
        .map(|x| x.parse::<i32>().unwrap())
        .collect();

    let mut dp = vec![vec![-1; k + 1]; n];
    println!("{}", calculate(&mut dp, &candies, n - 1, k));
    Ok(())
}

fn calculate(dp: &mut Vec<Vec<i32>>, candies: &Vec<i32>, n: usize, k: usize) -> i64 {
    if dp[n][k] != -1 {
        return dp[n][k] as i64;
    }
    if n == 0 {
        if k <= candies[n] as usize {
            return 1;
        }
        return 0;
    }

    let mut result = 0 as i64;
    for i in 0..candies[n]+1 {
        if k < i as usize {
            continue;
        }
        result += calculate(dp, candies, n - 1, k - i as usize);
        result %= 1_000_000_007;
    }
    dp[n][k] = result as i32;
    result
}
