#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

MOD = 10**9 + 7

# %%
N, S, K = map(int, read().split())

# %%
base = K * N * (N - 1) // 2
if base > S:
    print(0)
    exit()


# %%
S -= base
dp = [0] * (S + 1)
dp[0] = 1
for x in range(1, N + 1):
    for n in range(x, S + 1):
        dp[n] += dp[n - x]
        dp[n] %= MOD

print(dp[S])