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=[(0,0,0)]
INF=1<<60
s=[[INF]*n for _ in range(k+1)]
s[0][0]=0
while q:
  c,p,nk=heappop(q)
  if s[nk][p]<c:
    continue
  for v,nc in g[p]:
    if s[nk][v]>c+nc:
      s[nk][v]=c+nc
      heappush(q,(s[nk][v],v,nk))
    if nk<k:
      if s[nk+1][v]>c:
        s[nk+1][v]=c
        heappush(q,(s[nk+1][v],v,nk+1))
ans=INF
for i in range(k+1):
  ans=min(ans,s[i][-1])
print([-1,ans][ans<INF])