def generate(K):
    res=[]
    for i in range(1,10):
        for j in range(i+1,10):
            s=str(i)+str(j)*K
            res.append(int(s))
    return res

N=int(input())
K=1
A=[]
while(len(A)<=N):
    A+=generate(K)
    K+=1
A.sort()
print(A[N-1])