import sys
sys.setrecursionlimit(10000)
n,s,k=map(int,input().split())
res=s-k*n*(n-1)//2
MOD=10**9+7
if res<0:
    print(0)
    sys.exit()
dp=[[-1]*(n+1) for i in range(res+1)]
def rec(a,b):
    if a<0:
        return 0
    if dp[a][b]!=-1:
        return dp[a][b]
    if a==0 or b==1:
        dp[a][b]=1
        return 1
    x=rec(a,b-1)
    y=rec(a-b,b)
    z=(x+y)%MOD
    dp[a][b]=z
    return z
print(rec(res,n))