#include<stdio.h>
#include<vector>
using namespace std;
FILE*f=fopen("gardieni.in","r");
FILE*g=fopen("gardieni.out","w");
int x,n,t,s,sol[22],nr,a,b,c;
vector<int> v[1000002];
long long ss;
int main()
{
	fscanf(f,"%d%d",&n,&t);
	for(int i=1;i<=n;++i)
	{
		fscanf(f,"%d%d%d",&a,&b,&c);
		v[a].push_back (c);
		v[b].push_back (-c);
	}
	
	for(int i=1;i<=t;++i)
	{
		for(int j=0;j<v[i].size();++j)
			if(v[i][j]>0)
				sol[++nr]=v[i][j];
		s=2000000000;
		for(int j=1;j<=nr;++j)
			if(s>sol[j])
				s=sol[j];
		ss+=s;	
		for(int j=0;j<=v[i].size();++j)
			if(v[i][j]<0)
			{
				x=-v[i][j];
				int o;
				for(o=1;sol[o]!=x;++o);
				for(int ii=o+1;ii<=nr;++ii)
					sol[ii-1]=sol[ii];
				--nr;
			}
		
	}
	fprintf(g,"%lld",ss);
	
	
	fclose(f);
	fclose(g);
	return 0;
}