#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define R cin>>
#define Z class
#define ll long long
#define ln cout<<'\n'
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.10f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
template<Z A>void pr(A a){cout<<a;ln;}
template<Z A,Z B>void pr(A a,B b){cout<<a<<' ';pr(b);}
template<Z A,Z B,Z C>void pr(A a,B b,C c){cout<<a<<' ';pr(b,c);}
template<Z A,Z B,Z C,Z D>void pr(A a,B b,C c,D d){cout<<a<<' ';pr(b,c,d);}
template<Z A>void PR(A a,ll n){rep(i,n){if(i)cout<<' ';cout<<a[i];}ln;}
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}
const ll MAX=1e9+7,MAXL=1LL<<61,dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
typedef pair<ll,ll> P;

void Main() {
  ll n,m,k;
  cin >> n >> m >> k;
  vector<P> v[n+1];
  rep(i,m) {
    ll x,y,z;
    cin >> x >> y >> z;
    v[x-1].pb(P(y,z));
  }
  
  ll dp[n+1][2];
  rep(i,n+1)dp[i][0]=dp[i][1]=-MAXL;
  dp[0][1]=0;
  rep(i,n) {
    dp[i+1][0]=max(dp[i+1][0],dp[i][0]);
    dp[i+1][1]=max(dp[i+1][1],dp[i][0]-k);
    dp[i+1][0]=max(dp[i+1][0],dp[i][1]);
    dp[i+1][1]=max(dp[i+1][1],dp[i][1]-k);
    rep(j,v[i].size()) {
      dp[v[i][j].F][0]=max(dp[v[i][j].F][0],dp[i][0]+v[i][j].S-2*k+(v[i][j].F==n?k:0));
      dp[v[i][j].F][1]=max(dp[v[i][j].F][1],dp[i][0]+v[i][j].S-k+(v[i][j].F==n?k:0));
      dp[v[i][j].F][0]=max(dp[v[i][j].F][0],dp[i][1]+v[i][j].S-k+(v[i][j].F==n?k:0));
      dp[v[i][j].F][1]=max(dp[v[i][j].F][1],dp[i][1]+v[i][j].S-k+(v[i][j].F==n?k:0));
    }
  }
  pr(dp[n][0]);
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}