import heapq

n = int(input())

# Generate all valid (a, b) pairs where a < b
pairs = []
for a in range(1, 10):
    for b in range(a + 1, 10):
        pairs.append((a, b))

# Initialize the heap with the initial elements (c=0)
heap = []
for a, b in pairs:
    heapq.heappush(heap, (2, a, b, 0))  # (length, a, b, c)

current_step = 0
result = None

while heap:
    length, a, b, c = heapq.heappop(heap)
    current_step += 1
    if current_step == n:
        # Construct the result string
        result = str(a) + str(b) + str(b) * c
        break
    # Push the next element in this (a, b) sequence
    new_length = length + 1
    heapq.heappush(heap, (new_length, a, b, c + 1))

print(result)