def tri():
l = [1]
while True:
yield l
new_l = [l[i] + l[i+1] for i in range(len(l) -1)]
l = new_l
l.insert(0,1)
l.append(1)
n = int(input())
for i in tri():
n -= 1
if n < 0:
break
print(i)