#![allow(unused_imports,non_snake_case,dead_code)]
use std::{cmp::Reverse as Rev,collections::*,iter::*};
use proconio::{marker::*,*};


#[fastout]
fn main(){
    input!{
        n:usize,
        m:usize,
        k:usize,
        c:[i64;m],
        es:[(Usize1,Usize1);m],
    }

    let mut g=vec![vec![];n];
    for i in 0..m{
        let (u,v)=es[i];
        g[u].push((v,c[i]));
        g[v].push((u,c[i]));
    }

    const INF:i64=i64::MAX/64;
    let mut d=vec![[INF;4];n];

    let mut que=BinaryHeap::new();
    que.push((Rev(0),0,k));
    d[0][k]=0;
    
    while let Some((Rev(di),v,q))=que.pop(){
        if d[v][q]<di{
            continue;
        }

        let mut add=|nv:usize,nq:usize,cost:i64|{
            if d[nv][nq]>cost+di{
                d[nv][nq]=cost+di;
                que.push((Rev(cost),nv,nq));
            }
        };

        for &(nv,cost) in &g[v]{
            // クーポンを使う
            if q>0{
                add(nv,q-1,0);
            }
            
            // 使わない
            add(nv,q,cost);
        }
    }

    let ans=*d[n-1].iter().min().unwrap();

    if ans==INF{
        println!("-1");
    } else{
        println!("{}",ans);
    }
}