h

#include<bits/stdc++.h>
using namespace std;
struct node{
       int b, e, t;
}sugg[5001];
bool cmp(node x, node y){
    return x.e<y.e;
}
int main(){
    int b,e,t;
    int n,h;
    cin>>n>>h;
    for(int i=1;i<=h;i++){
        cin>>sugg[i].b>>sugg[i].e>>sugg[i].t;
    }
    sort(sugg+1,sugg+1+h,cmp);
    int res=0;
    int road[10000]={0};
       for(int i=1;i<=h;i++){
        for(int j=sugg[i].e;j>=sugg[i].b;j--){
            if(road[j]==1){
                sugg[i].t--;
            }
        }
        for(int j=sugg[i].e;j>=sugg[i].b;j--){
            if(sugg[i].t==0){
                break;
            }
            if(road[j]==1){
                sugg[i].t--;
 
            }else{
                sugg[i].t--;
                road[j]=1;
                res++;
            }
        }
       }
       cout<<res;
}