#include < cstdio >
#include < cstring >
#include < cstdlib >
using   namespace  std;

struct  node{
     int  x,y,z;
}m[ 3100 ];
int  N,M;
int  ans;
int  c[ 5100 ];
int  a[ 5100 ];
inline  int  lowbit( int  x)
{  return  x ^ (x & (x - 1 )); }
int  cmp( const   void *  A, const   void *  B)
{
    node  * aa = (node * )A, * bb = (node * )B;
     if (aa -> y != bb -> y)  return  aa -> y - bb -> y;
     else   return  aa -> x - bb -> x;
}
int  getsum( int  x)
{
     int  sum = 0 ;
     while (x){
        sum += c[x];
        x -= lowbit(x);
    }
     return  sum;
}
void  modify( int  x)
{
     while (x <= N){
        c[x] ++ ;
        x += lowbit(x);
    }
}
int  main()
{
    scanf( " %d%d " , & N, & M);
     for ( int  i = 1 ;i <= M; ++ i)
        scanf( " %d%d%d " , & m[i].x, & m[i].y, & m[i].z);
    qsort(m + 1 ,M, sizeof (node),cmp);
    memset(a, 0 , sizeof (a));
    ans = 0 ;
     for ( int  i = 1 ;i <= M; ++ i){
         int  val = m[i].z - (getsum(m[i].y) - getsum(m[i].x - 1 ));
         for ( int  j = m[i].y;j >= m[i].x; -- j){
             if (val <= 0 )  break ;
             if (a[j] == 0 ){
                a[j] = 1 ;
                modify(j);
                val -- ;
                ans ++ ;
            }
        }
    }
    printf( " %d\n " ,ans);
     return   0 ;
}