import sys
input=lambda: sys.stdin.readline().rstrip()
n,s,k=map(int,input().split())
mod=10**9+7
s-=n*(n-1)//2*k
if s<0:
  print(0)
else:
  DP=[1]*(s+1)
  for i in range(2,n+1):
    for j in range(i,s+1):
      DP[j]=(DP[j]+DP[j-i])%mod
  print(DP[s])