import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

class StarrySkyTreeL {
  public int M, H, N;
  public long[] st;
  public long[] plus;
  public long I = Long.MAX_VALUE/4; // I+plus<long
  
  public StarrySkyTreeL(int n)
  {
      N = n;
      M = Integer.highestOneBit(Math.max(n-1, 1))<<2;
      H = M>>>1;
      st = new long[M];
      plus = new long[H];
  }
  
  public StarrySkyTreeL(long[] a)
  {
      N = a.length;
      M = Integer.highestOneBit(Math.max(N-1, 1))<<2;
      H = M>>>1;
      st = new long[M];
      for(int i = 0;i < N;i++){
          st[H+i] = a[i];
      }
      plus = new long[H];
      Arrays.fill(st, H+N, M, I);
      for(int i = H-1;i >= 1;i--)propagate(i);
  }
  
  private void propagate(int i)
  {
      st[i] = Math.min(st[2*i], st[2*i+1]) + plus[i];
  }
  
  public void add(int l, int r, long v){ if(l < r)add(l, r, v, 0, H, 1); }
  
  private void add(int l, int r, long v, int cl, int cr, int cur)
  {
      if(l <= cl && cr <= r){
          if(cur >= H){
              st[cur] += v;
          }else{
              plus[cur] += v;
              propagate(cur);
          }
      }else{
          int mid = cl+cr>>>1;
          if(cl < r && l < mid){
              add(l, r, v, cl, mid, 2*cur);
          }
          if(mid < r && l < cr){
              add(l, r, v, mid, cr, 2*cur+1);
          }
          propagate(cur);
      }
  }
  
  public long min(int l, int r){ return l >= r ? I : min(l, r, 0, H, 1);}
  
  private long min(int l, int r, int cl, int cr, int cur)
  {
      if(l <= cl && cr <= r){
          return st[cur];
      }else{
          int mid = cl+cr>>>1;
          long ret = I;
          if(cl < r && l < mid){
              ret = Math.min(ret, min(l, r, cl, mid, 2*cur));
          }
          if(mid < r && l < cr){
              ret = Math.min(ret, min(l, r, mid, cr, 2*cur+1));
          }
          return ret + plus[cur];
      }
  }
  
  public void fall(int i)
  {
      if(i < H){
          if(2*i < H){
              plus[2*i] += plus[i];
              plus[2*i+1] += plus[i];
          }
          st[2*i] += plus[i];
          st[2*i+1] += plus[i];
          plus[i] = 0;
      }
  }
  
  public int firstle(int l, long v) {
      int cur = H+l;
      for(int i = 1, j = Integer.numberOfTrailingZeros(H)-1;i <= cur;j--){
          fall(i);
          i = i*2|cur>>>j&1;
      }
      while(true){
          fall(cur);
          if(st[cur] <= v){
              if(cur < H){
                  cur = 2*cur;
              }else{
                  return cur-H;
              }
          }else{
              cur++;
              if((cur&cur-1) == 0)return -1;
              cur = cur>>>Integer.numberOfTrailingZeros(cur);
          }
      }
  }
  
  public int lastle(int l, long v) {
      int cur = H+l;
      for(int i = 1, j = Integer.numberOfTrailingZeros(H)-1;i <= cur;j--){
          fall(i);
          i = i*2|cur>>>j&1;
      }
      while(true){
          fall(cur);
          if(st[cur] <= v){
              if(cur < H){
                  cur = 2*cur+1;
              }else{
                  return cur-H;
              }
          }else{
              if((cur&cur-1) == 0)return -1;
              cur = cur>>>Integer.numberOfTrailingZeros(cur);
              cur--;
          }
      }
  }
  
  public void addx(int l, int r, long v){
      if(l >= r)return;
      while(l != 0){
          int f = l&-l;
          if(l+f > r)break;
          if(f == 1){
              st[(H+l)/f] += v;
          }else{
              plus[(H+l)/f] += v;
          }
          l += f;
      }
      
      while(l < r){
          int f = r&-r;
          if(f == 1){
              st[(H+r)/f-1] += v;
          }else{
              plus[(H+r)/f-1] += v;
          }
          r -= f;
      }
  }
  
  public long minx(int l, int r){
      long lmin = I;
      if(l >= r)return lmin;
      if(l != 0){
          for(int d = 0;H>>>d > 0;d++){
              if(d > 0){
                  int id = (H+l-1>>>d);
                  lmin += plus[id];
              }
              if(l<<~d<0 && l+(1<<d) <= r){
                  long v = st[H+l>>>d];
                  if(v < lmin)lmin = v;
                  l += 1<<d;
              }
          }
      }
      long rmin = I;
      for(int d = 0;H>>>d > 0;d++){
          if(d > 0 && r < H)rmin += plus[H+r>>>d];
          if(r<<~d<0 && l < r){
              long v = st[(H+r>>>d)-1];
              if(v < rmin)rmin = v;
              r -= 1<<d;
          }
      }
      long min = Math.min(lmin, rmin);
      return min;
  }
  
  public long[] toArray() { return toArray(1, 0, H, new long[H]); }
  
  private long[] toArray(int cur, int l, int r, long[] ret)
  {
      if(r-l == 1){
          ret[cur-H] = st[cur];
      }else{
          toArray(2*cur, l, l+r>>>1, ret);
          toArray(2*cur+1, l+r>>>1, r, ret);
          for(int i = l;i < r;i++)ret[i] += plus[cur];
      }
      return ret;
  }
}



public class Main {


  private static void solve() {
    int n = ni();
    int m = ni();
    
    List<List<Integer>> add = new ArrayList<>();
    List<List<int[]>> del = new ArrayList<>();
    for (int i = 0; i <= n; i ++) {
      add.add(new ArrayList<>());
      del.add(new ArrayList<>());
    }
    for (int i = 0; i < m; i ++) {
      int l = ni();
      int r = ni();
      int a = ni();
      add.get(l).add(-a);
      del.get(r).add(new int[] {l, -a});
    }

    long ret = 0;
    StarrySkyTreeL sst = new StarrySkyTreeL(n + 1);
    for (int i = 1; i <= n; i ++) {
      for (int a : add.get(i)) {
        sst.add(0, i, a);
      }
      long now = sst.min(0, i);
      sst.add(i, i + 1, now);
      ret = Math.max(ret, -now);
      
      for (int[] v : del.get(i)) {
        sst.add(0, v[0], -v[1]);
      }
    }
    System.out.println(ret);
  }

  public static void main(String[] args) {
    new Thread(null, new Runnable() {
      @Override
      public void run() {
        long start = System.currentTimeMillis();
        String debug = args.length > 0 ? args[0] : null;
        if (debug != null) {
          try {
            is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
          } catch (Exception e) {
            throw new RuntimeException(e);
          }
        }
        reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
        solve();
        out.flush();
        tr((System.currentTimeMillis() - start) + "ms");
      }
    }, "", 64000000).start();
  }

  private static java.io.InputStream is = System.in;
  private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
  private static java.util.StringTokenizer tokenizer = null;
  private static java.io.BufferedReader reader;

  public static String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }

  private static double nd() {
    return Double.parseDouble(next());
  }

  private static long nl() {
    return Long.parseLong(next());
  }

  private static int[] na(int n) {
    int[] a = new int[n];
    for (int i = 0; i < n; i++)
      a[i] = ni();
    return a;
  }

  private static char[] ns() {
    return next().toCharArray();
  }

  private static long[] nal(int n) {
    long[] a = new long[n];
    for (int i = 0; i < n; i++)
      a[i] = nl();
    return a;
  }

  private static int[][] ntable(int n, int m) {
    int[][] table = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[i][j] = ni();
      }
    }
    return table;
  }

  private static int[][] nlist(int n, int m) {
    int[][] table = new int[m][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[j][i] = ni();
      }
    }
    return table;
  }

  private static int ni() {
    return Integer.parseInt(next());
  }

  private static void tr(Object... o) {
    if (is != System.in)
      System.out.println(java.util.Arrays.deepToString(o));
  }
}


Measured memory_bytes: 111880