#![allow(unused_imports, dead_code, unused_macros, unused_variables, non_snake_case, unused_parens)]
use proconio::{input,marker::{Bytes, Chars, Usize1,Isize1}};
use std::ops::*;
use std::cmp::*;
use std::mem::swap;
use std::collections::*;

const MOD:u64 = 1_000_000_007;
const INF:usize = 0x3fff_ffff_ffff_ffff;
const YES:&str="Yes";const NO:&str="No";macro_rules!yesno{($var:expr) => {if $var{println!("{}",YES);}else{println!("{}",NO);}}}

macro_rules! min {($a:expr $(,)*) => {{$a}};($a:expr, $b:expr $(,)*) => {{std::cmp::min($a, $b)}};($a:expr, $($rest:expr),+ $(,)*) => {{std::cmp::min($a, min!($($rest),+))}};}
macro_rules! max {($a:expr $(,)*) => {{$a}};($a:expr, $b:expr $(,)*) => {{std::cmp::max($a, $b)}};($a:expr, $($rest:expr),+ $(,)*) => {{std::cmp::max($a, max!($($rest),+))}};}
macro_rules! chmin {($base:expr, $($cmps:expr),+ $(,)*) => {{let cmp_min = min!($($cmps),+);if $base > cmp_min {$base = cmp_min;true} else {false}}};}
macro_rules! chmax {($base:expr, $($cmps:expr),+ $(,)*) => {{let cmp_max = max!($($cmps),+);if $base < cmp_max {$base = cmp_max;true} else {false}}};}
macro_rules! mulvec {($x:expr; $s:expr) => {vec![$x; $s]};($x:expr; $s0:expr; $( $s:expr );+) => {mulvec![vec![$x; $s0]; $( $s );+ ]};}
macro_rules! outputln {($var:expr)=>{println!("{}",$var)};($var:expr,$($vars:expr),+)=>{print!("{} ",$var);outputln!($($vars),+);};}
macro_rules! debug {($($a:expr),* $(,)*) => {eprintln!(concat!($("| ",stringify!($a), "={:?} "),*, "|"),$(&$a),*);};}


fn solve() {
    input! {
        n: usize,
        m: usize,
        k: usize,
		C: [usize;m],
		UV:[(Usize1, Usize1); m],
    }
	let mut edge = vec![vec![];n];
	for i in 0..m {
		let (u,v) = UV[i];
		edge[u].push((v, C[i]));
		edge[v].push((u, C[i]));
	}
	let mut dist = vec![INF; n*(k+1)];
	let mut visit = vec![false; n*(k+1)];
	let mut que = BinaryHeap::new();
	que.push((Reverse(0), 0));
	dist[0] = 0;
	let limit = n*(k+1);
	while let Some((Reverse(d), v)) = que.pop() {
		if visit[v] {continue}
		visit[v] = true;
		let offset = v/n * n;
		for &(u, c) in &edge[v%n] {
			let u = u + offset;
			if !visit[u] && dist[u] > d+c {
				que.push((Reverse(d+c), u));
				dist[u] = d+c;
			}
			if u+n < limit && !visit[u+n] && dist[u+n] > d {
				que.push((Reverse(d), u+n));
				dist[u+n] = d;
			}
		}
	}
	let ans = (0..=k).map(|i| dist[n*i+n-1]).min().unwrap();
	if ans == INF {
		outputln!(-1);
	}else{
		outputln!(ans);
	}
}

fn main() {
    std::thread::Builder::new()
        .stack_size(128 * 1024 * 1024)
        .spawn(|| solve()).unwrap()
        .join().unwrap();
}