def main1(n,m,a,lrp):
  g=[[] for _ in range(n+1)]
  for l,r,p in lrp:
    # 区間[l,r]を作る→次作れるのは[r+1,x]
    g[l-1].append([r,p])
  inf=float('inf')
  seen=[-inf]*n*2
  # seen[0*n+v]:現在vにいて、左に黒線ありのときの最大値
  # seen[1*n+v]:現在vにいて、左に黒線なしのときの最大値
  seen[0]=0
  ans=0
  for v in range(n):
    if seen[v]!=-inf:
      if v+1==n:
        ans=max(ans,seen[v])
      elif seen[n+v+1]<seen[v]:
        seen[n+v+1]=seen[v]
      for nv,np in g[v]:
        if nv==n:
          ans=max(ans,seen[v]+np)
        else:
          if seen[nv]<seen[v]+np-a:
            seen[nv]=seen[v]+np-a
    if seen[n+v]!=-inf:
      if v+1==n:
        ans=max(ans,seen[n+v])
      elif seen[n+v+1]<seen[n+v]:
        seen[n+v+1]=seen[n+v]
      for nv,np in g[v]:
        if nv==n:
          ans=max(ans,seen[n+v]+np-a)
        else:
          if seen[nv]<seen[n+v]+np-a-a:
            seen[nv]=seen[n+v]+np-a-a
  return ans

if __name__=='__main__':
  n,m,a=map(int,input().split())
  lrp=[list(map(int,input().split())) for _ in range(m)]
  ret1=main1(n,m,a,lrp)
  print(ret1)