N,M,a = map(int,input().split())
D = [[] for _ in range(N+1)]
for _ in range(M):
    l,r,p = map(int,input().split())
    D[r].append((l,p))
dp = [0]*(N+1)
for i in range(1,N+1):
    dp[i] = dp[i-1]
    if len(D[i])>0:
        for l,p in D[i]:
            dp[i] = max(dp[i],dp[l-1]+p)
L = [0]*(N+1)
d = dp[N]
for i in range(N,0,-1):
    if d==dp[i]>dp[i-1]:
        r = i
        for l0,p0 in D[i]:
            if dp[i]==dp[l0-1]+p0:
                l = l0
                p = p0
                break
        d -= p
        L[r] = 1
        L[l-1] = 1
L[0] = 0
L[N] = 0
ans = max(0,dp[N]-sum(L)*a)
print(ans)