N = int(input())
c = 0
nums = []
while len(nums) < N:
    for a in range(1, 10):
        for b in range(a+1, 10):
            X = 10*a+b
            for _ in range(c):
                X = 10*X + b
            nums.append(X)
    c += 1
nums.sort()
print(nums[N-1])