#include <cstdio>
#include <algorithm>
using namespace std;
const int N = 50000;
struct need {
    int b, e, t, l;
    bool operator <(const need &x) const {
        return x.e == e ? x.b > b : x.e > e;
    }
} a[N];
int n, h, s;
int main() {
    freopen("trees.in", "r", stdin);
    freopen("trees.out", "w", stdout);
    scanf("%d", &n);
    scanf("%d", &h);
    for(int i=1; i<=h; i++)
        scanf("%d %d %d", &a[i].b, &a[i].e, &a[i].t);
    sort(a+1, a+h+1);
    //for(int i=1; i<=h; i++)
    //    fprintf(stderr, "%d %d %d\n", a[i].b, a[i].e, a[i].t);
    for(int i=1; i<=h; i++) {
        for(int j=a[i].b; j<=a[i].e; j++)
            if(a[j].l)
                a[i].t--;
        int k=a[i].e;
        for(int j=1; j<=a[i].t; j++) {
            while(a[k].l) k--;
            a[k].l = 1;
            s++;
        }
    }
    printf("%d\n", s);
    return 0;
}