#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<iomanip>
#include<math.h>
#include<complex>
#include<queue>
#include<deque>
#include<stack>
#include<map>
#include<set>
#include<bitset>
#include<functional>
#include<assert.h>
#include<numeric>
using namespace std;
#define REP(i,m,n) for(int i=(int)(m) ; i < (int) (n) ; ++i )
#define rep(i,n) REP(i,0,n)
typedef long long ll;


ll dp[101010][2];
int main(){
	ll n,m;
	cin>>n>>m;
	assert(n>=2&&n<=100000);
	assert(2<=m&&m<=100000&&m<=n*(n+1)/2);
	ll a;
	cin>>a;
	assert(1<=a&&a<=1000000000);
	vector<pair<int,long long>> v[n];
	set<pair<int,int>> st;
	rep(i,m){
		int x,y,z;
		cin>>x>>y>>z;
		assert(1<=x&&x<=y&&y<=n);
		assert(st.count({x,y})==0);
		assert(1<=z&&z<=1000000000);
		st.insert({x,y});
		--x;--y;

		v[y].emplace_back(x,z);
	}
	rep(i,n){
		dp[i+1][0]=max(dp[i][0],dp[i][1]);
		dp[i+1][1]=max(dp[i][0],dp[i][1])-a;
		for(auto p : v[i]){
			dp[i+1][1]=max(dp[i+1][1],dp[p.first][1]+p.second-a);
		}
	}
	cout<<max(dp[n][1]+a,dp[n][0])<<endl;
	return 0;
}