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#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,b) for (int i = (a); i <= (b); ++i)
#define REPD(i,a,b) for (int i = (a); i >= (b); --i)
#define FORI(i,n) REP(i,1,n)
#define FOR(i,n) REP(i,0,int(n)-1)
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define vi vector<int>
#define ll long long
#define SZ(x) int((x).size())
#define DBG(v) cerr << #v << " = " << (v) << endl;
#define FOREACH(i,t) for (typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define fi first
#define se second

pair<int,int> all[2000200];

int main() {
	int n,m;
	scanf("%d%d", &n, &m);
	FOR(i,m) {
		int le,ri,col;
		scanf("%d%d%d", &le, &ri, &col);
		all[2*i  ] = mp(le-1, -col);
		all[2*i+1] = mp(ri  ,  col);
	}
	m *= 2;
	sort(all, all+m);
	int y=0, b=0, r=0;
	int res=0;
	FOR(i,m) {
		if (r==0 && y>0 && b>0) {
			res += all[i].fi - all[i-1].fi;
		}
		switch(all[i].se) {
			case -3: r++; break;
			case -2: b++; break;
			case -1: y++; break;
			case  1: y--; break;
			case  2: b--; break;
			case  3: r--; break;
		}
	}
	printf("%d\n", res);
	return 0;
}