import heapq as h
g={}
n,m,k=map(int,input().split())
c=list(map(int,input().split()))
for i in range(1,n+1):g[str(i)]={}
for i in range(m):
 u,v=input().split()
 g[u][v]=g[v][u]=c[i]
s="1";e=str(n)
d={i:float('inf')for i in g};d[s]=0
p={i:None for i in g}
q=[(0,s)]
while q:
 cd,cn=h.heappop(q)
 if cd>d[cn]:continue
 if cn==e:break
 for nb,w in g[cn].items():
  di=cd+w
  if di<d[nb]:d[nb]=di;p[nb]=cn;h.heappush(q,(di,nb))
if d[e]==float('inf'):print(-1)
else:
 pe=[]
 c=e
 while c!=s:
  pr=p[c]
  pe.append((pr,c,g[pr][c]))
  c=pr
 pe.sort(key=lambda x:x[2],reverse=True)
 tk=pe[:min(k,len(pe))]
 print(d[e]-sum(e[2]for e in tk))