N = int(input())

l = []
for i in range(1,9):
    for j in range(i + 1,10):
        l.append(i * 10 + j)
l.sort()
n = len(l)
N -= 1
q = N // n
r = N % n
a = l[r]
b = a % 10
for _ in range(q):
    a *= 10
    a += b
print(a)