N,S,K=map(int,raw_input().split())
S-=K*N*(N-1)/2
if S < 0:
    print 0
    exit()

dp=[[-1 for i in range(S+1)] for k in range(N+1)]
mod=1000000007

def rec(N,S):
    if S<0:
        return 0
    if dp[N][S]!=-1:
        return dp[N][S]
    if N==1:
        dp[N][S]=1
        return dp[N][S]
    dp[N][S]=rec(N,S-N)+rec(N-1,S)
    dp[N][S]%=mod
    #print N,S,dp[N][S]
    return dp[N][S]

print rec(N,S)