Educational Codeforces Round 53 (Rated for Div. 2) A. Diverse Substring

A. Diverse Substring

 

You are given a string ss, consisting of nn lowercase Latin letters.

A substring of string ss is a continuous segment of letters from ss. For example, "defor" is a substring of "codeforces" and "fors" is not.

The length of the substring is the number of letters in it.

Let's call some string of length nn diverse if and only if there is no letter to appear strictly more than n2n2 times. For example, strings "abc" and "iltlml" are diverse and strings "aab" and "zz" are not.

Your task is to find any diverse substring of string ss or report that there is none. Note that it is not required to maximize or minimize the length of the resulting substring.

Input

The first line contains a single integer nn (1≤n≤10001≤n≤1000) — the length of string ss.

The second line is the string ss, consisting of exactly nn lowercase Latin letters.

Output

Print "NO" if there is no diverse substring in the string ss.

Otherwise the first line should contain "YES". The second line should contain any diverse substring of string ss.

Examples

input

Copy

10
codeforces

output

Copy

YES
code

input

Copy

5
aaaaa

output

Copy

NO

题意：在字符串s里找一个子串s1，s1长度为L，其中s1里任意一个元素出现次数不超过L/2次，问你能不能构造出这样一个子串。

思路：推理一下规律可以发现，长串必然由短串构成，所以找最短的串即可，再推可以发现长度为2刚好满足要求，且要保证每个字符只出现一次。

所以判断相邻元素是否有不同的，有则输出，否则判定NO。

#include 
#define ll long long
using namespace std;
int n,flag;
char s[1010];
int main()
{
    while(~scanf("%d",&n))
    {
        scanf("%s",s);
        flag=0;
        for(int i=1;i