import heapq

def main():
    N = int(input())
    heap = []
    
    # Generate all possible (a, b) pairs with a < b and push their initial values into the heap
    for a in range(1, 10):
        for b in range(a + 1, 10):
            initial_num = str(10 * a + b)
            num_tuple = (len(initial_num),) + tuple(map(int, initial_num))
            heapq.heappush(heap, (num_tuple, a, b, 0))
    
    current_count = 0
    result = ""
    while heap:
        num_tuple, a, b, c = heapq.heappop(heap)
        current_count += 1
        if current_count == N:
            # Convert the tuple back to the string representation
            result = ''.join(map(str, num_tuple[1:]))
            break
        # Generate the next number by appending b to the current number
        new_num_str = ''.join(map(str, num_tuple[1:])) + str(b)
        new_num_tuple = (len(new_num_str),) + tuple(map(int, new_num_str))
        heapq.heappush(heap, (new_num_tuple, a, b, c + 1))
    
    print(result)

if __name__ == "__main__":
    main()