N = int(input())
if N<100:
    ans = 0
    for i in range(10,N+1):
        if i%3>0:continue
        if (i//10+i%10)%3==0:
            ans += 1
else:
    D = len(str(N))
    A = [0]+list(map(int,list(str(N))))
    dp = [[0 for _ in range(2)] for _ in range(D+1)]
    if A[1]%3==0:
        dp[1][0] = 1
    for i in range(10):
        if i<A[1] and i%3==0:
            dp[1][1] += 1
    for i in range(2,D+1):
        if A[i]%3==0:
            dp[i][0] = dp[i-1][0]
        cnt = 0
        for j in range(10):
            if j<A[i] and j%3==0:
                cnt += 1
        dp[i][1] = dp[i-1][0]*cnt+dp[i-1][1]*4
    ans = dp[D][0]+dp[D][1]-4
    for i in range(10,100):
        if (i//10)%3==1 and (i%10)%3==2:
            ans += 1
        elif (i//10)%3==2 and (i%10)%3==1:
            ans += 1 
print(ans)