문제
https://www.acmicpc.net/problem/1065
풀이

코드
def check(n):
if n < 100: return True
arr = [int(i) for i in str(n)]
diff = arr[1] - arr[0]
for i in range(2, len(arr)):
if (arr[i] - arr[i-1]) != diff: return False
return True
def answer(n):
count = 0
for i in range(1, n+1):
if check(i): count += 1
return count
n = int(input())
print(answer(n))