Balanced Substring ----思维

B. Balanced Substring

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

You are given a string s consisting only of characters 0 and 1. A substring [l, r] of s is a string s_ls_l + 1s_l + 2... s_r, and its length equals to r - l + 1. A substring is called balanced if the number of zeroes (0) equals to the number of ones in this substring.

You have to determine the length of the longest balanced substring of s.

Input

The first line contains n (1 ≤ n ≤ 100000) — the number of characters in s.

The second line contains a string s consisting of exactly n characters. Only characters 0 and 1 can appear in s.

Output

If there is no non-empty balanced substring in s, print 0. Otherwise, print the length of the longest balanced substring.

Examples

Input

Copy

8
11010111

Output

Copy

4

Input

Copy

3
111

Output

Copy

0

Note

In the first example you can choose the substring [3, 6]. It is balanced, and its length is 4. Choosing the substring [2, 5] is also possible.

In the second example it's impossible to find a non-empty balanced substring.

易错点：将0这个地方的位置视为0.

然后遇到1，+1，遇到0，-1.如果和之前出现过，那么就说明中间这段区间是平衡的。

代码：

#include
using namespace std;
int dp[200011];
int main()
{
    int n;
    string h;
    scanf("%d",&n);
    int sum=100010;
    int ans=0;
    cin>>h;
    memset(dp,-1,sizeof(dp));
    dp[100010]=0;
    for(int i=0;i