#yuki269
import sys

n,s,k=map(int,raw_input().split())
s-=k*n*(n-1)/2
if s<0:
 print 0
 sys.exit()
dp=[1 for i in xrange(s+1)]
for i in xrange(2,n):
 for j in xrange(i,s+1):
  dp[j]+=dp[j-i]
print sum(dp[s::-n])%(10**9+7)