#[allow(unused_imports)]
use itertools::Itertools;
#[allow(unused_imports)]
use proconio::{
    input,
    marker::{Chars, Isize1, Usize1},
};
#[allow(unused_imports)]
use std::{
    cmp::Reverse,
    cmp::{max, min},
    collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, VecDeque},
    process::exit,
};
const DXY: [(isize, isize); 4] = [(0, 1), (0, -1), (1, 0), (-1, 0)];
const FIRST_VALUE: usize = 1_000_000_000;
const MOD: usize = 1_000_000_007;
#[allow(non_snake_case)]
fn main() {
    input! {
        N: usize,
        mut S: isize,
        K: usize,
    }
    S -= (K * N * (N - 1) / 2) as isize;
    if S < 0 {
        println!("0");
        exit(0);
    }

    let mut dp = vec![vec![0; S as usize + 1]; N + 1];
    // dp[i][j] := jをi分割するときの総数
    dp[0][0] = 1;
    for i in (1..=N) {
        for j in (0..=(S as usize)) {
            if j >= i {
                dp[i][j] = dp[i - 1][j] + dp[i][j - i];
                dp[i][j] %= MOD;
            } else {
                dp[i][j] = dp[i - 1][j];
            }
        }
    }
    println!("{}", dp[N][S as usize]);
}