# Original solution
import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 7)

N,M = list(map(int,input().split()))
LRA = [[int(x) for x in row.split()] for row in sys.stdin.readlines()]

R_to_LA = [[] for _ in range(N+1)]
for L,R,A in LRA:
    R_to_LA[R].append((L,A))

INF = 10 ** 18

size = 1<<18
data = [0] * (2*size)
lazy = [0] * (2*size)
left_end = [None] * (2*size)
right_end = [None] * (2*size)
q = [1]
left_end[1] = 0
right_end[1] = size
for n in range(1,size):
    L,R = left_end[n],right_end[n]
    M = (L+R)//2
    left_end[2*n] = L
    right_end[2*n] = M
    left_end[2*n+1] = M
    right_end[2*n+1] = R

def get_max(R):
    q = [1]
    ret = -INF
    while q:
        qq = []
        for i in q:
            iL = left_end[i]
            iR = right_end[i]
            if iR <= R:
                # 完全に含まれている
                x = data[i] + lazy[i]
                if ret < x:
                    ret = x
            elif R<=iL:
                # 完全に無関係
                pass
            else:
                # 部分的に交わっている
                j = i<<1; k = j+1
                lazy[j] += lazy[i]; lazy[k] += lazy[i]
                lazy[i] = 0
                qq.append(2*i); qq.append(2*i+1)
        q = qq
    return ret

def add(L,R,x):
    q = [1]
    q1 = []
    while q:
        qq = []
        for i in q:
            iL = left_end[i]
            iR = right_end[i]
            if L <= iL and iR <= R:
                # 完全に含まれている
                lazy[i] += x
            elif iR<=L or R<=iL:
                pass
            else:
                # 部分的に交わっている
                q1.append(i)
                j = i<<1; k = j+1
                lazy[j] += lazy[i]; lazy[k] += lazy[i]
                lazy[i] = 0
                qq.append(j)
                qq.append(k)
        q = qq
    for i in reversed(q1):
        j = i<<1; k = j+1
        data[i] = max(data[j]+lazy[j],data[k]+lazy[k])

for R in range(1,N+1):
    x = get_max(R)
    add(R,R+1,x)
    for L,A in R_to_LA[R]:
        add(L,R+1,A)

for n in range(size):
    lazy[2*n] += lazy[n]
    lazy[2*n+1] += lazy[n]

answer = max(lazy[size:])
print(answer)

# Optimized solution
import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 7)

N,M = list(map(int,input().split()))
LRA = [[int(x) for x in row.split()] for row in sys.stdin.readlines()]

R_to_LA = [[] for _ in range(N+1)]
for L,R,A in LRA:
    R_to_LA[R].append((L,A))

INF = 10 ** 18

size = 1<<18
data = [0] * (2*size)
lazy = [0] * (2*size)
left_end = [None] * (2*size)
right_end = [None] * (2*size)
left_end[1] = 0
right_end[1] = size
for n in range(1,size):
    L,R = left_end[n],right_end[n]
    M = (L+R)//2
    left_end[2*n] = L
    right_end[2*n] = M
    left_end[2*n+1] = M
    right_end[2*n+1] = R

def add(L,R,x):
    q = [1]
    q1 = []
    while q:
        qq = []
        for i in q:
            iL = left_end[i]
            iR = right_end[i]
            if L <= iL and iR <= R:
                # 完全に含まれている
                lazy[i] += x
            elif iR<=L or R<=iL:
                pass
            else:
                # 部分的に交わっている
                q1.append(i)
                j = i<<1; k = j+1
                lazy[j] += lazy[i]; lazy[k] += lazy[i]
                lazy[i] = 0
                qq.append(j)
                qq.append(k)
        q = qq
    for i in reversed(q1):
        j = i<<1; k = j+1
        data[i] = max(data[j]+lazy[j],data[k]+lazy[k])

for R in range(1,N+1):
    x = data[1] + lazy[1]
    add(R,R+1,x)
    for L,A in R_to_LA[R]:
        add(L,R+1,A)

for n in range(size):
    lazy[2*n] += lazy[n]
    lazy[2*n+1] += lazy[n]

answer = max(lazy[size:])
print(answer)