#[allow(unused_imports)]
use std::cmp::{max, min, Ordering};
#[allow(unused_imports)]
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
#[allow(unused_imports)]
use std::iter::FromIterator;
// input macro
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}

struct Unionfind {
    data: Vec<i32>,
    cnt: u32,
}

impl Unionfind {
    fn new(n: usize) -> Unionfind {
        Unionfind {
            data: vec![-1; n],
            cnt: n as u32,
        }
    }
    fn root(&mut self, x: usize) -> usize {
        let r;
        if self.data[x] < 0 {
            r = x
        } else {
            let nx = self.data[x] as usize;
            r = self.root(nx);
            self.data[x] = r as i32;
        }
        r
    }
    fn unite(&mut self, x: usize, y: usize) {
        let nx = self.root(x);
        let ny = self.root(y);
        if x != y {
            let (nx, ny) = if self.data[ny] < self.data[nx] {
                (ny, nx)
            } else {
                (nx, ny)
            };
            self.data[nx] += self.data[ny];
            self.data[ny] = nx as i32;
            self.cnt -= 1;
        }
    }
    fn same(&mut self, x: usize, y: usize) -> bool {
        self.root(x) == self.root(y)
    }
    fn size(&mut self, x: usize) -> i32 {
        let nx = self.root(x);
        -self.data[nx]
    }
    fn size1(&mut self) -> u32 {
        self.cnt
    }
}

fn main() {
    input!{
        n: usize,
        m: usize,
        ab: [(usize1, usize1); m],
    }
    let mut cnt = 0;
    for i in (0..m) {
        let mut uf = Unionfind::new(n);
        for j in (0..m) {
            if i != j {
                if uf.same(ab[j].0, ab[j].1) == false {
                    uf.unite(ab[j].0, ab[j].1);
                }
            }
        }
        if uf.size1() != 1 {
            cnt += 1;
        }
    }
    println!("{}", cnt);
}


Measured memory_bytes: 4352