Problem:
Score : 100 points

Problem Statement

You are given a 4-character string S consisting of uppercase English letters.
Determine if S consists of exactly two kinds of characters which both appear twice in S.

Constraints

The length of S is 4.

S consists of uppercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If S consists of exactly two kinds of characters which both appear twice in S, print Yes; otherwise, print No.

Sample Input 1

ASSA

Sample Output 1

Yes

S consists of A and S which both appear twice in S.

Sample Input 2

STOP

Sample Output 2

No

Sample Input 3

FFEE

Sample Output 3

Yes

Sample Input 4

FREE

Sample Output 4

No

Solution in Rust (1.42.0) (judge verdict: Accepted)

use text_io::*;
use std::collections::*;
use std::process::exit;
use std::cmp::*;

fn main() {
    let mut n:String = read!();
    let mut v:Vec<char> = n.chars().collect();
    if (v[0]==v[1]&&v[1]!=v[2]&&v[2]==v[3]) || (v[0]==v[2]&&v[1]!=v[2]&&v[1]==v[3]) || (v[0]==v[3]&&v[0]!=v[2]&&v[2]==v[1]) {
        println!("Yes");
    }
    else {
        println!("No");
    }
}