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