#include <bits/stdc++.h>
using namespace std;
#define N 30005
typedef struct Node{
int s,e,k;
}Node;
Node node[N];
int n,m,res,cnt;
bool vis[N];
bool cmp(const Node &A,const Node &B){
return A.e<B.e;
}
int main(){
scanf("%d%d",&n,&m);
for(int i=1;i<=m;++i){
scanf("%d%d%d",&node[i].s,&node[i].e,&node[i].k);
}
std::sort(node+1,node+1+m,cmp);
for(int i=1;i<=m;++i){
res=0;
for(int j=node[i].s;j<=node[i].e;++j){
if(vis[j])++res;
}
if(res>=node[i].k)continue;
for(int j=node[i].e;j>=node[i].s;--j){
if(!vis[j]){
vis[j]=true;
++res;
++cnt;
}
if(res==node[i].k)break;
}
}
printf("%d",cnt);
}
/*
Good Luck & Have Fun >_<
┏┓ ┏┓
┏┛┻━━━┛┻┓
┃ ┃
┃ ━ ┃
┃ ┳┛ ┗┳ ┃
┃ ┃
┃ ┻ ┃
┃ ┃
┗━┓ ┏━┛Codes are far away from bugs with the animal protecting
┃ ┃ 神兽保佑, 代码无bug
┃ ┃
┃ ┗━━━┓
┃ ┣┓
┃ ┏┛
┗┓┓┏━┳┓┏┛
┃┫┫ ┃┫┫
┗┻┛ ┗┻┛ o-| ̄|_
*/