import java.io.*;
import java.util.*;


public class Main_yukicoder844 {

	private static Scanner sc;
	private static Printer pr;

	private static void solve() {
		int n = sc.nextInt();
		int m = sc.nextInt();
		int a = sc.nextInt();

		List<List<Pair>> edges = new ArrayList<>(n);
		for (int i = 0; i < n; i++) {
			edges.add(new ArrayList<>());
		}
		for (int i = 0; i < m; i++) {
			int l = sc.nextInt();
			int r = sc.nextInt();
			int p = sc.nextInt();
			
			edges.get(l - 1).add(new Pair(r, p));
		}

		long[][] dp = new long[2][n + 1];
//		Arrays.fill(dp[0], Long.MIN_VALUE);
//		Arrays.fill(dp[1], Long.MIN_VALUE);
//		dp[0][n] = dp[1][n] = 0;
		for (int i = n - 1; i > 0; i--) {
			dp[0][i] = Math.max(dp[0][i + 1], dp[1][i + 1]);
			dp[1][i] = Math.max(dp[0][i + 1] - a, dp[1][i + 1] - a);
			for (Pair e : edges.get(i)) {
				dp[1][i] = Math.max(dp[1][i], dp[1][e.a] + e.b - a);
			}
		}
		
		dp[1][0] = Math.max(dp[0][1], dp[1][1]);
		for (Pair e : edges.get(0)) {
			dp[1][0] = Math.max(dp[1][0], dp[1][e.a] + e.b);
		}

		pr.println(dp[1][0]);
	}

	static class Pair implements Comparable<Pair> {
		int a;
		int b;

		Pair(int a, int b) {
			this.a = a;
			this.b = b;
		}

		@Override
		public int compareTo(Pair o) {
			int result = Integer.compare(a, o.a);
			if (result == 0) {
				result = Integer.compare(b, o.b);
			}
			return result;
		}

		@Override
		public int hashCode() {
			final int prime = 31;
			int result = a;
			result = prime * result + b;
			return result;
		}

		@Override
		public boolean equals(Object obj) {
			if (this == obj)
				return true;
			if (!(obj instanceof Pair))
				return false;

			Pair o = (Pair) obj;
			return a == o.a && b == o.b;
		}

		@Override
		public String toString() {
			//			Pair [xxx, xxxx]
			StringBuilder stmp = new StringBuilder(32);
			stmp.append("Pair [");
			stmp.append(a);
			stmp.append(',');
			stmp.append(' ');
			stmp.append(b);
			stmp.append(']');

			return stmp.toString();
		}
	}

	// ---------------------------------------------------
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		pr = new Printer(System.out);
			
		solve();
			
		pr.close();
		sc.close();
	}

	static class Printer extends PrintWriter {
		Printer(OutputStream out) {
			super(out);
		}
	}
}