# import sys # input = sys.stdin.readline # import pypyjit # pypyjit.set_param('max_unroll_recursion=-1') def mp():return map(int,input().split()) def lmp():return list(map(int,input().split())) def mps(A):return [tuple(map(int, input().split())) for _ in range(A)] def stoi(LIST):return list(map(int,LIST)) def itos(LIST):return list(map(str,LIST)) def bitA(X,A):return X & 1< y:x,y = y,x if x != 1 and y != n: if y-x == 1: print(0) else: step = y - 1 - (x+1) jump = 0 ans = 0 while step >= 0: ans += combination(step + jump, jump, mod) ans %= mod step -= 3 jump += 1 print(ans % mod) elif x == 1: step = y-1 jump = 0 ans = 0 while step >= 0: ans += combination(step+jump,jump,mod) ans %= mod step -= 3 jump += 1 print(ans%mod) else: step = n-x jump = 0 ans = 0 while step >= 0: ans += combination(step+jump,jump,mod) ans %= mod step -= 3 jump += 1 print(ans%mod)