#include<algorithm>
#include<cstdio>
using namespace std;
int k,v[1000005],a,b,n,i,j,m;
long long s;
int main()
{
	freopen("gardieni.in","r",stdin);
	freopen("gardieni.out","w",stdout);
	scanf("%d %d",&n,&m);
	for (i=1;i<=n;i++)
	{
		scanf("%d %d %d",&a,&b,&k);
		for (j=a;j<=b;j++) if (v[j]==0) s+=k,v[j]=k;else if (k<v[j]) s-=v[j],v[j]=k,s+=k;
	}
	printf("%lld\n",s);
	return 0;
}