Problem:
Score : 700 points

Problem Statement

Given is a sequence of N digits a_1a_2\ldots a_N, where each element is 1, 2, or 3.
Let x_{i,j} defined as follows:

x_{1,j} := a_j \quad (1 \leq j \leq N)

x_{i,j} := | x_{i-1,j} - x_{i-1,j+1} | \quad (2 \leq i \leq N and 1 \leq j \leq N+1-i)

Find x_{N,1}.

Constraints

2 \leq N \leq 10^6

a_i = 1,2,3 (1 \leq i \leq N)

Input

Input is given from Standard Input in the following format:

N
a_1a_2\ldotsa_N

Output

Print x_{N,1}.

Sample Input 1

4
1231

Sample Output 1

1

x_{1,1},x_{1,2},x_{1,3},x_{1,4} are respectively 1,2,3,1.

x_{2,1},x_{2,2},x_{2,3} are respectively |1-2| = 1,|2-3| = 1,|3-1| = 2.

x_{3,1},x_{3,2} are respectively |1-1| = 0,|1-2| = 1.

Finally, x_{4,1} = |0-1| = 1, so the answer is 1.

Sample Input 2

10
2311312312

Sample Output 2

0

Solution in Python (3.4.3) (judge verdict: Accepted)

import sys
n=int(input())
s=input()
frac=[0]*(n+1)
for i in range(1,n+1):
    k=i
    frac[i]=frac[i-1]
    while k%2==0:
        k//=2
        frac[i]+=1

ans=0
for i in range(n):
    if int(s[i])==2 and frac[n-1]-frac[i]-frac[n-1-i]==0:
        ans^=1

if ans==1: print(1)
elif "2" in s: print(0)
else:
    ans=0
    for i in range(n):
        if int(s[i])==3 and frac[n-1]-frac[i]-frac[n-1-i]==0:
            ans^=1
    print(ans*2)