from heapq import*
(n,m,k),c,*e=[[*map(int,s.split())]for s in open(0)]
g=[[]for _ in range(n)]
for i,(u,v)in zip(c,e):
  g[u-1]+=(v-1,i),
  g[v-1]+=(u-1,i),
q=[(0,0)]
INF=1<<60
s=[INF]*n
s[0]=0
while q:
  c,p=heappop(q)
  if s[p]<c:
    continue
  for v,nc in g[p]:
    if s[v]>c+nc:
      s[v]=c+nc
      heappush(q,(s[v],v))
if s[-1]==INF:
  exit(print(-1))
p=n-1
c=s[p]
d=[]
while p:
  for v,nc in g[p]:
    if s[v]+nc==s[p]:
      d+=nc,
      p=v
      break
d.sort()
for _ in range(k):
  d.pop()
print(sum(d))