#include<stdio.h>
FILE*f=fopen("gardieni.in","r");
FILE*g=fopen("gardieni.out","w");
long T;
long long S;
long t[1000003],a,b,c;
void update()
   {
    long i;
    for(i=a;i<=b;++i)
       if(t[i]>c || t[i]==0)
         {
          S=S-t[i]+c;
          t[i]=c;
         }
   }
int main()
   {
    long n,i;
    fscanf(f,"%ld %ld",&n,&T);
    for(i=1;i<=n;++i)
        {
         fscanf(f,"%ld %ld %ld",&a,&b,&c);
         update();
         }
    fprintf(g,"%lld\n",S);
    return 0;
   }