#include <bits/stdc++.h>

using namespace std;

/*********************************************/
/// INPUT / OUTPUT
ifstream f("gardieni.in");
ofstream g("gardieni.out");
/*********************************************/
/// GLOBAL DECLARATIONS

int n, t, ans;

int a, b, c;

unordered_map <int, int> mapa;
/*********************************************/
/// FUNCTIONS

void ReadInput();
void Solution();
void Output();
/*********************************************/

///----------------------------------------------------------------
inline void ReadInput()
{
    f >> n >> t;
}
///----------------------------------------------------------------
inline void Solution()
{
    while(t)
    {
        f >> a >> b >> c;
        for(int i = a ; i <= b ; ++ i)
        {
         if(!mapa[i]) mapa[i] = c;
         else mapa[i] = min(mapa[i], c);
        }
        t--;
    }

    for(auto it: mapa)
    {
        ans+= it.second;
    }
}
///----------------------------------------------------------------
inline void Output()
{
    g << ans;
}
///----------------------------------------------------------------
int main()
{
    ReadInput();
    Solution();
    Output();
    return 0;
}