Baekjoon1065

def solve(N) :

    steps = []
    
    if N < 100 :
        print(N)

    else : 
     answer = 99

     for a in range(100, N+1) :

           a = str(a)

           for b in range(len(a)-1) :
                step = int(a[b]) - int(a[b+1])
                steps.append(step)

           if steps.count(steps[0]) == len(steps) :
               answer += 1
            
           steps = []

     print(answer)

n = int(input())
solve(n)