import heapq

def main():
    N = int(input().strip())
    heap = []
    
    # Generate all possible (a, b) pairs where a < b
    for a in range(1, 10):
        for b in range(a + 1, 10):
            s = f"{a}{b}"
            # Push the tuple (length, string, a, b, c)
            heapq.heappush(heap, (len(s), s, a, b, 0))
    
    count = 0
    result = ""
    while heap:
        current = heapq.heappop(heap)
        length, s, a, b, c = current
        count += 1
        
        if count == N:
            result = s
            break
        
        # Generate the next number by appending b
        new_s = s + str(b)
        new_length = length + 1
        heapq.heappush(heap, (new_length, new_s, a, b, c + 1))
    
    print(result)

if __name__ == "__main__":
    main()