import heapq

n = int(input())

heap = []
# Generate all possible (a, b) pairs and their initial numbers
for a in range(1, 10):
    for b in range(a + 1, 10):
        num_str = f"{a}{b}"
        heapq.heappush(heap, (len(num_str), num_str, a, b))

current = None
for _ in range(n):
    current = heapq.heappop(heap)
    length, num_str, a, b = current
    next_num_str = num_str + str(b)
    heapq.heappush(heap, (len(next_num_str), next_num_str, a, b))

print(current[1])