M=10**9+7
d=Array.new(4+N=gets.to_i){[0]*4}
d[1][1]=d[2][2]=d[3][3]=1
-~N.times{|i|(1..3).map{|j|d[i+j][j]+=(d[i].sum-d[i][j])%M}}
p d[N].sum%M