#![allow(unused_imports, unused_macros)]

use kyoproio::*;
use std::{
    collections::*,
    io::{self, prelude::*},
    iter,
    mem::{replace, swap},
};

fn run<I: Input, O: Write>(mut kin: I, mut out: O) {
    const INF: i64 = 1 << 60;
    let (t, n, m): (i32, usize, usize) = kin.input();
    let mut g = LabeledGraph::builder(n + 1);
    for (u, v, w) in kin.iter::<(usize, usize, i64)>().take(m) {
        g.edge(u, v, w);
        if t == 0 {
            g.edge(v, u, w);
        }
    }
    let g = g.build();
    let mut dist = vec![vec![INF; n + 1]; n + 1];
    let mut par = vec![vec![0; n + 1]; n + 1];
    for s in 1..=n {
        dist[s][s] = 0;
        let mut que = BinaryHeap::new();
        que.push((0, s));
        while let Some((d, u)) = que.pop() {
            let d = -d;
            if d > dist[s][u] {
                continue;
            }
            for &(v, w) in &g[u] {
                let dc = dist[s][u] + w;
                if dc < dist[s][v] {
                    dist[s][v] = dc;
                    par[s][v] = u;
                    que.push((-dc, v));
                }
            }
        }
    }
    let mut ans = INF;
    if t == 0 {
        for s in 1..=n {
            for u in 1..=n {
                for &(v, w) in &g[u] {
                    if par[s][u] == v || par[s][v] == u {
                        continue;
                    }
                    ans = ans.min(dist[s][u] + w + dist[s][v]);
                }
            }
        }
    } else {
        for s in 1..=n {
            for t in 1..=n {
                if s != t {
                    ans = ans.min(dist[s][t] + dist[t][s]);
                }
            }
        }
        
    }
    if ans == INF {
        ans = -1;
    }
    outln!(out, "{}", ans);
}

pub struct Graph(LabeledGraph<()>);
impl Graph {
    pub fn builder(n: usize) -> GraphBuilder {
        GraphBuilder(LabeledGraph::builder(n))
    }
    pub fn len(&self) -> usize {
        self.0.len()
    }
}
impl std::ops::Index<usize> for Graph {
    type Output = [usize];
    fn index(&self, u: usize) -> &Self::Output {
        unsafe { std::mem::transmute(self.0.index(u)) }
    }
}
pub struct GraphBuilder(LabeledGraphBuilder<()>);
impl GraphBuilder {
    pub fn edge(&mut self, u: usize, v: usize) {
        self.0.edge(u, v, ());
    }
    pub fn build(&mut self) -> Graph {
        Graph(self.0.build())
    }
}
pub struct LabeledGraph<T> {
    edges: Box<[(usize, T)]>,
    heads: Box<[usize]>,
}
impl<T: Clone> LabeledGraph<T> {
    pub fn builder(n: usize) -> LabeledGraphBuilder<T> {
        LabeledGraphBuilder {
            nodes: Vec::new(),
            heads: vec![!0; n],
        }
    }
    pub fn len(&self) -> usize {
        self.heads.len() - 1
    }
}
impl<T> std::ops::Index<usize> for LabeledGraph<T> {
    type Output = [(usize, T)];
    fn index(&self, u: usize) -> &Self::Output {
        &self.edges[self.heads[u]..self.heads[u + 1]]
    }
}
pub struct LabeledGraphBuilder<T> {
    nodes: Vec<((usize, T), usize)>,
    heads: Vec<usize>,
}
impl<T: Clone> LabeledGraphBuilder<T> {
    pub fn edge(&mut self, u: usize, v: usize, l: T) {
        self.nodes.push(((v, l), self.heads[u]));
        self.heads[u] = self.nodes.len() - 1;
    }
    pub fn build(&mut self) -> LabeledGraph<T> {
        let mut edges = Vec::with_capacity(self.nodes.len());
        let mut heads = Vec::with_capacity(self.heads.len() + 1);
        for &(mut h) in &self.heads {
            heads.push(edges.len());
            while let Some((e, next)) = self.nodes.get(h) {
                edges.push(e.clone());
                h = *next;
            }
        }
        heads.push(edges.len());
        LabeledGraph {
            edges: edges.into(),
            heads: heads.into(),
        }
    }
}

// -----------------------------------------------------------------------------
fn main() -> io::Result<()> {
    std::thread::Builder::new()
        .stack_size(64 * 1024 * 1024)
        .spawn(|| {
            run(
                KInput::new(io::stdin().lock()),
                io::BufWriter::new(io::stdout().lock()),
            )
        })?
        .join()
        .unwrap();
    Ok(())
}

#[macro_export]
macro_rules! out {
    ($($arg:tt)*) => { write!($($arg)*).unwrap(); }
}
#[macro_export]
macro_rules! outln {
    ($dst:expr $(, $($arg:tt)*)?) => {{
        writeln!($dst $(, $($arg)*)?).unwrap();
        if cfg!(debug_assertions) { $dst.flush().unwrap(); }
    }}
}
#[macro_export]
macro_rules! eout {
    ($($arg:tt)*) => { if cfg!(debug_assertions) { eprintln!($($arg)*); } }
}
#[macro_export]
macro_rules! kdbg {
    ($($v:expr),*) => { if cfg!(debug_assertions) { dbg!($($v),*) } else { ($($v),*) } }
}

pub mod kyoproio {
    use std::{
        io::prelude::*,
        iter::FromIterator,
        marker::PhantomData,
        mem::{self, MaybeUninit},
        str,
    };

    pub trait Input {
        fn bytes(&mut self) -> &[u8];
        fn str(&mut self) -> &str {
            str::from_utf8(self.bytes()).unwrap()
        }
        fn input<T: InputItem>(&mut self) -> T {
            T::input(self)
        }
        fn iter<T: InputItem>(&mut self) -> Iter<T, Self> {
            Iter(self, PhantomData)
        }
        fn seq<T: InputItem, B: FromIterator<T>>(&mut self, n: usize) -> B {
            self.iter().take(n).collect()
        }
    }
    pub struct KInput<R> {
        src: R,
        buf: Vec<u8>,
        pos: usize,
        len: usize,
    }
    impl<R: Read> KInput<R> {
        pub fn new(src: R) -> Self {
            Self {
                src,
                buf: vec![0; 1 << 16],
                pos: 0,
                len: 0,
            }
        }
        fn read(&mut self) -> usize {
            if self.pos > 0 {
                self.buf.copy_within(self.pos..self.len, 0);
                self.len -= self.pos;
                self.pos = 0;
            } else if self.len >= self.buf.len() {
                self.buf.resize(2 * self.buf.len(), 0);
            }
            let n = self.src.read(&mut self.buf[self.len..]).unwrap();
            self.len += n;
            n
        }
    }
    impl<R: Read> Input for KInput<R> {
        fn bytes(&mut self) -> &[u8] {
            loop {
                while let Some(d) = self.buf[self.pos..self.len]
                    .iter()
                    .position(u8::is_ascii_whitespace)
                {
                    let p = self.pos;
                    self.pos += d + 1;
                    if d > 0 {
                        return &self.buf[p..p + d];
                    }
                }
                if self.read() == 0 {
                    return &self.buf[mem::replace(&mut self.pos, self.len)..self.len];
                }
            }
        }
    }
    pub struct Iter<'a, T, I: ?Sized>(&'a mut I, PhantomData<*const T>);
    impl<'a, T: InputItem, I: Input + ?Sized> Iterator for Iter<'a, T, I> {
        type Item = T;
        fn next(&mut self) -> Option<T> {
            Some(self.0.input())
        }
        fn size_hint(&self) -> (usize, Option<usize>) {
            (!0, None)
        }
    }
    pub trait InputItem: Sized {
        fn input<I: Input + ?Sized>(src: &mut I) -> Self;
    }
    impl InputItem for Vec<u8> {
        fn input<I: Input + ?Sized>(src: &mut I) -> Self {
            src.bytes().to_owned()
        }
    }
    macro_rules! from_str {
        ($($T:ty)*) => {
            $(impl InputItem for $T {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    src.str().parse::<$T>().unwrap()
                }
            })*
        }
    }
    from_str!(String char bool f32 f64);
    macro_rules! parse_int {
        ($($I:ty: $U:ty)*) => {
            $(impl InputItem for $I {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    let f = |s: &[u8]| s.iter().fold(0, |x, b| 10 * x + (b & 0xf) as $I);
                    let s = src.bytes();
                    if let Some((&b'-', t)) = s.split_first() { -f(t) } else { f(s) }
                }
            }
            impl InputItem for $U {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    src.bytes().iter().fold(0, |x, b| 10 * x + (b & 0xf) as $U)
                }
            })*
        }
    }
    parse_int!(isize:usize i8:u8 i16:u16 i32:u32 i64:u64 i128:u128);
    macro_rules! tuple {
        ($H:ident $($T:ident)*) => {
            impl<$H: InputItem, $($T: InputItem),*> InputItem for ($H, $($T),*) {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    ($H::input(src), $($T::input(src)),*)
                }
            }
            tuple!($($T)*);
        };
        () => {}
    }
    tuple!(A B C D E F G);
    macro_rules! array {
        ($($N:literal)*) => {
            $(impl<T: InputItem> InputItem for [T; $N] {
                fn input<I: Input + ?Sized>(src: &mut I) -> Self {
                    let mut arr = MaybeUninit::uninit();
                    let ptr = arr.as_mut_ptr() as *mut T;
                    unsafe {
                        for i in 0..$N {
                            ptr.add(i).write(src.input());
                        }
                        arr.assume_init()
                    }
                }
            })*
        }
    }
    array!(1 2 3 4 5 6 7 8);
}