import heapq

n = int(input())

heap = []
# Generate all a and b pairs where a < b
for a in range(1, 10):
    for b in range(a + 1, 10):
        initial = str(a) + str(b)
        heapq.heappush(heap, (2, initial, a, b, 1))

count = 0
result = ""
while heap:
    length, current, a, b, k = heapq.heappop(heap)
    count += 1
    if count == n:
        result = current
        break
    # Generate next number by appending b
    next_str = current + str(b)
    next_length = length + 1
    heapq.heappush(heap, (next_length, next_str, a, b, k + 1))

print(result)