#yuki844
n,m,a=map(int,input().split())
e=[[] for i in range(n)]
for i in range(m):
 x,y,z=map(int,input().split())
 e[y-1].append([x-1,z])
dp=[0]*(n+1)
res=0
for i in range(n):
 dp[i+1]=res-a
 for p in e[i]:
  dp[i+1]=max(dp[i+1],dp[p[0]]+p[1]-(a if i!=n-1 else 0))
 res=max(res,dp[i+1])
print(res)