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#include <iostream>
#include <cstdint>
#include <vector>
#include <utility>
#include <algorithm>
#include <bitset>
#include <limits>
#include <unordered_map>

using namespace std;


struct bla{
    int position;
    int colour;
    int operation; // +1 add, -1 remove
    bool operator < (const bla &rhs) const {
     return (position<rhs.position);
    }
};


int main(){
    std::ios::sync_with_stdio(false);
    cin.tie(0);

    int n, m;
    cin >>n>>m;

    vector <bla> tab;
    tab.reserve(m*2);
    while (m-->0){
        int l, r, k;
        cin>>l>>r>>k;
        tab.push_back(bla{l,k,1});
        tab.push_back(bla{r+1,k,-1});
    }
    sort (begin(tab), end(tab));

    int counter =0;
    int last_position =1;
    int colours[3]={0,0,0};
    for (auto it = begin(tab); it!=end(tab);++it){
        if ((colours[0]>0)&&(colours[1]>0)&&(colours[2]==0))
            counter +=   it->position - last_position;
        colours[it->colour-1] += it->operation;
        last_position = it->position;
    }
    cout<< counter<<endl;


    return 0;
}