fn main() {
    inputv! {
        t:usize,
        n:usize,m:usize,
    }
    let mut graph = vec![vec![]; n * 2];
    for i in 0..m {
        inputv! {
            u:usize,v:usize,w:isize
        }
        graph[2 * (u - 1) + 1].push((2 * (v - 1), w));
        if t == 0 {
            graph[2 * (v - 1)].push((2 * (u - 1) + 1, w));
        }
    }
    for i in 0..n {
        graph[2 * i].push((2 * i + 1, 0));
    }
    let mut ans = isize::max_value();
    for i in 0..n {
        let r = dijkstra(&graph, 2 * i + 1);
        ans = std::cmp::min(ans, r[2 * i]);
    }
    println!("{}", if ans == isize::max_value() { -1 } else { ans });
}

//https://github.com/manta1130/competitive-template-rs

use graph::*;
use input::*;

pub mod graph {
    use std::cmp;
    use std::collections::BinaryHeap;

    #[allow(clippy::ptr_arg)]
    pub fn bellman_ford(graph: &Vec<Vec<(usize, isize)>>, dist: &mut [Option<isize>]) -> Vec<bool> {
        let mut neg_flag = vec![false; dist.len()];

        for _ in 0..graph.len() {
            for (from, v) in graph.iter().enumerate() {
                for e in v.iter() {
                    let cost = e.1;
                    let to = e.0;
                    if let Some(x) = dist[from] {
                        if dist[to].is_none() {
                            dist[to] = Some(x + cost);
                        } else if let Some(y) = dist[to] {
                            if y > x + cost {
                                dist[to] = Some(x + cost);
                            }
                        }
                    }
                }
            }
        }

        for _ in 0..graph.len() {
            for (from, v) in graph.iter().enumerate() {
                for e in v.iter() {
                    let cost = e.1;
                    let to = e.0;
                    if let Some(x) = dist[from] {
                        if dist[to].is_none() {
                            dist[to] = Some(x + cost);
                            neg_flag[to] = true;
                        } else if let Some(y) = dist[to] {
                            if y > x + cost {
                                dist[to] = Some(x + cost);
                                neg_flag[to] = true;
                            }
                        }
                    }
                    if neg_flag[from] {
                        neg_flag[to] = true;
                    }
                }
            }
        }
        neg_flag
    }

    #[allow(clippy::ptr_arg)]
    pub fn dijkstra(graph: &Vec<Vec<(usize, isize)>>, start: usize) -> Vec<isize> {
        let mut heap = BinaryHeap::new();
        let mut dist = vec![isize::max_value(); graph.len()];
        dist[start] = 0;

        heap.push((0_isize, start));

        while !heap.is_empty() {
            let e = heap.pop().unwrap();
            if e.0.wrapping_neg() > dist[e.1] {
                continue;
            }
            for next_e in graph[e.1].iter() {
                if dist[next_e.0] > next_e.1 + dist[e.1] {
                    dist[next_e.0] = next_e.1 + dist[e.1];
                    heap.push(((dist[e.1] + next_e.1).wrapping_neg(), next_e.0));
                }
            }
        }
        dist
    }

    pub fn warshall_floyd(graph: &mut [&mut [isize]]) {
        for k in 0..graph.len() {
            for i in 0..graph.len() {
                for j in 0..graph.len() {
                    graph[i][j] = cmp::min(graph[i][j], graph[i][k] + graph[k][j]);
                }
            }
        }
    }
}
pub mod input {
    use std::cell::RefCell;
    use std::io;
    pub const SPLIT_DELIMITER: char = ' ';
    pub use std::io::prelude::*;

    #[macro_export]
    thread_local! {
        pub static INPUT_BUFFER:RefCell<std::collections::VecDeque<String>>=RefCell::new(std::collections::VecDeque::new());
    }

    #[macro_export]
    macro_rules! input_internal {
        ($x:ident : $t:ty) => {
            INPUT_BUFFER.with(|p| {
                if p.borrow().len() == 0 {
                    let temp_str = input_line_str();
                    let mut split_result_iter = temp_str
                        .split(SPLIT_DELIMITER)
                        .map(|q| q.to_string())
                        .collect::<std::collections::VecDeque<_>>();
                    p.borrow_mut().append(&mut split_result_iter)
                }
            });
            let mut buf_split_result = String::new();
            INPUT_BUFFER.with(|p| buf_split_result = p.borrow_mut().pop_front().unwrap());
            let $x: $t = buf_split_result.parse().unwrap();
        };
        (mut $x:ident : $t:ty) => {
            INPUT_BUFFER.with(|p| {
                if p.borrow().len() == 0 {
                    let temp_str = input_line_str();
                    let mut split_result_iter = temp_str
                        .split(SPLIT_DELIMITER)
                        .map(|q| q.to_string())
                        .collect::<std::collections::VecDeque<_>>();
                    p.borrow_mut().append(&mut split_result_iter)
                }
            });
            let mut buf_split_result = String::new();
            INPUT_BUFFER.with(|p| buf_split_result = p.borrow_mut().pop_front().unwrap());
            let mut $x: $t = buf_split_result.parse().unwrap();
        };
    }

    #[macro_export]
    macro_rules! inputv {
    ($i:ident : $t:ty) => {
        input_internal!{$i : $t}
    };
    (mut $i:ident : $t:ty) => {
        input_internal!{mut $i : $t}
    };
    ($i:ident : $t:ty $(,)*) => {
            input_internal!{$i : $t}
    };
    (mut $i:ident : $t:ty $(,)*) => {
            input_internal!{mut $i : $t}
    };
    (mut $i:ident : $t:ty,$($q:tt)*) => {
            input_internal!{mut $i : $t}
            inputv!{$($q)*}
    };
    ($i:ident : $t:ty,$($q:tt)*) => {
            input_internal!{$i : $t}
            inputv!{$($q)*}
    };
}

    pub fn input_all() {
        INPUT_BUFFER.with(|p| {
            if p.borrow().len() == 0 {
                let mut temp_str = String::new();
                std::io::stdin().read_to_string(&mut temp_str).unwrap();
                let mut split_result_iter = temp_str
                    .split_whitespace()
                    .map(|q| q.to_string())
                    .collect::<std::collections::VecDeque<_>>();
                p.borrow_mut().append(&mut split_result_iter)
            }
        });
    }

    pub fn input_line_str() -> String {
        let mut s = String::new();
        io::stdin().read_line(&mut s).unwrap();
        s.trim().to_string()
    }

    #[allow(clippy::match_wild_err_arm)]
    pub fn input_vector<T>() -> Vec<T>
    where
        T: std::str::FromStr,
    {
        let mut v: Vec<T> = Vec::new();

        let s = input_line_str();
        let split_result = s.split(SPLIT_DELIMITER);
        for z in split_result {
            let buf = match z.parse() {
                Ok(r) => r,
                Err(_) => panic!("Parse Error",),
            };
            v.push(buf);
        }
        v
    }

    #[allow(clippy::match_wild_err_arm)]
    pub fn input_vector_row<T>(n: usize) -> Vec<T>
    where
        T: std::str::FromStr,
    {
        let mut v = Vec::with_capacity(n);
        for _ in 0..n {
            let buf = match input_line_str().parse() {
                Ok(r) => r,
                Err(_) => panic!("Parse Error",),
            };
            v.push(buf);
        }
        v
    }

    pub trait ToCharVec {
        fn to_charvec(&self) -> Vec<char>;
    }

    impl ToCharVec for String {
        fn to_charvec(&self) -> Vec<char> {
            self.to_string().chars().collect::<Vec<_>>()
        }
    }
}