Problem:
Print a Frame

Draw a frame which has a height of H cm and a width of W cm. For example, the following figure shows a frame which has a height of 6 cm and a width of 10 cm.

##########
#........#
#........#
#........#
#........#
##########

Input

The input consists of multiple datasets. Each dataset consists of two integers H and W separated by a single space.

The input ends with two 0 (when both H and W are zero).

Output

For each dataset, print the frame made of '#' and '.'.

Print a blank line after each dataset.

Constraints

3 ≤ H ≤ 300

3 ≤ W ≤ 300

Sample Input

3 4
5 6
3 3
0 0

Sample Output

####
#..#
####

######
#....#
#....#
#....#
######

###
#.#
###

Solution in Rust (judge verdict: Accepted)

use std::io;

fn main() {
    loop {
        let (h, w) = input();
        if (h, w) == (0, 0) {
            break;
        }

        for i in 0..h {
            for j in 0..w {
                let s = if i == 0 || i == h - 1 || j == 0 || j == w - 1 {
                    "#"
                } else {
                    "."
                };
                print!("{}", s);
            }
            println!("");
        }
        println!("");
    }
}

fn input() -> (i32, i32) {
    let mut s = String::new();
    io::stdin().read_line(&mut s).expect("");
    let mut iter = s.trim().split_whitespace();

    let a: i32 = iter.next().unwrap().parse().unwrap();
    let b: i32 = iter.next().unwrap().parse().unwrap();

    (a, b)
}