n=gets.to_i
if n<3
  p n
  exit 0
end

memo=[]
memo[0]=1
memo[1]=0

M=1000000007

for i in 2 .. n
  memo[i] = memo[i-2] + memo[i-3]
  memo[i] %= M
end

p (memo[n]+memo[n-1]+memo[n-2])%M