#include <stdio.h>

long n,t,a[1000010],x,y,c;
long long s;

int main()
{
	freopen("gardieni.in","r",stdin);
	freopen("gardieni.out","w",stdout);
	scanf("%d%d",&n,&t);
	int i,j;
	s=0;
	for (i=1; i<=n; ++i)
	{
		scanf("%d%d%d",&x,&y,&c);
		for (j=x; j<=y; ++j)
		{
			if (a[j]>c || a[j]==0) 
			{
				s=(long long)s-a[j]+c;
				a[j]=c;
			}
		}
	}
	printf("%lld\n",s);
	return 0;
}