MOD=10**9+7
N,S,K=map(int, input().split())
S-=N*(N-1)//2*K
if S<0:
    print(0)
    exit()

dp=[0]*(S+1)
dp[0]=1
for i in range(1,N+1):
    for j in range(S+1-i):
        dp[j+i]+=dp[j]
        dp[j+i]%=MOD
print(dp[-1])