Problem:
Score : 200 points

Problem Statement

The postal code in Atcoder Kingdom is A+B+1 characters long, its (A+1)-th character is a hyphen -, and the other characters are digits from 0 through 9.

You are given a string S. Determine whether it follows the postal code format in Atcoder Kingdom.

Constraints

1≤A,B≤5

|S|=A+B+1

S consists of - and digits from 0 through 9.

Input

Input is given from Standard Input in the following format:

A B
S

Output

Print Yes if S follows the postal code format in AtCoder Kingdom; print No otherwise.

Sample Input 1

3 4
269-6650

Sample Output 1

Yes

The (A+1)-th character of S is -, and the other characters are digits from 0 through 9, so it follows the format.

Sample Input 2

1 1
---

Sample Output 2

No

S contains unnecessary -s other than the (A+1)-th character, so it does not follow the format.

Sample Input 3

1 2
7444

Sample Output 3

No

Solution in Rust (1.15.1) (judge verdict: Accepted)

#!/usr/bin/env run-cargo-script

#![allow(unused_imports)]

use std::cmp;
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
use std::fmt;
use std::io::{self, BufWriter, Read, StdinLock, Write};
use std::ops::{Add, Div, Mul, Sub};
use std::str::{self, FromStr};

fn solve(a: usize, b: usize, s: String) -> bool {
    let s = s.as_bytes();
    s.len() == a + b + 1
        && s.iter()
            .enumerate()
            .all(|(i, &c)| i == a && c == b'-' || i != a && b'0' <= c && c <= b'9')
}

fn main() {
    let stdin = io::stdin();
    let mut sc = Scanner::new(stdin.lock().bytes());
    println!(
        "{}",
        if solve(sc.next(), sc.next(), sc.next()) {
            "Yes"
        } else {
            "No"
        }
    );
}

struct Scanner<R: Read> {
    buf: Vec<u8>,
    bytes: io::Bytes<R>,
}

#[allow(dead_code)]
impl<R: Read> Scanner<R> {
    fn new(bytes: io::Bytes<R>) -> Self {
        Scanner {
            buf: Vec::with_capacity(1024),
            bytes: bytes,
        }
    }

    fn next<T: FromStr>(&mut self) -> T
    where
        <T as FromStr>::Err: fmt::Debug,
    {
        let buf = &mut self.buf;
        buf.clear();
        self.bytes
            .by_ref()
            .map(Result::unwrap)
            .skip_while(|&c| c == ' ' as u8 || c == '\n' as u8)
            .take_while(|&c| !(c == ' ' as u8 || c == '\n' as u8))
            .foreach(|c| buf.push(c));
        str::from_utf8(&buf).unwrap().parse().unwrap()
    }

    fn vec<T: FromStr>(&mut self, n: usize) -> Vec<T>
    where
        <T as FromStr>::Err: fmt::Debug,
    {
        (0..n).map(|_| self.next()).collect()
    }

    fn pairs<T1: FromStr, T2: FromStr>(&mut self, n: usize) -> Vec<(T1, T2)>
    where
        <T1 as FromStr>::Err: fmt::Debug,
        <T2 as FromStr>::Err: fmt::Debug,
    {
        (0..n).map(|_| (self.next(), self.next())).collect()
    }

    fn trios<T1: FromStr, T2: FromStr, T3: FromStr>(&mut self, n: usize) -> Vec<(T1, T2, T3)>
    where
        <T1 as FromStr>::Err: fmt::Debug,
        <T2 as FromStr>::Err: fmt::Debug,
        <T3 as FromStr>::Err: fmt::Debug,
    {
        (0..n)
            .map(|_| (self.next(), self.next(), self.next()))
            .collect()
    }

    fn mat<T: FromStr>(&mut self, m: usize, n: usize) -> Vec<Vec<T>>
    where
        <T as FromStr>::Err: fmt::Debug,
    {
        (0..m).map(|_| self.vec(n)).collect()
    }

    fn strings_as_mat<T, F: FnMut(u8) -> T>(&mut self, h: usize, mut f: F) -> Vec<Vec<T>> {
        (0..h)
            .map(|_| {
                self.bytes
                    .by_ref()
                    .map(Result::unwrap)
                    .skip_while(|&c| c == ' ' as u8 || c == '\n' as u8)
                    .take_while(|&c| !(c == ' ' as u8 || c == '\n' as u8))
                    .map(&mut f)
                    .collect()
            })
            .collect()
    }
}

trait Foreach {
    type Item;
    fn foreach<F: FnMut(Self::Item)>(self, f: F);
}

impl<T, I: Iterator<Item = T>> Foreach for I {
    type Item = T;

    fn foreach<F: FnMut(T)>(self, mut f: F) {
        self.fold((), move |(), x| f(x));
    }
}