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#include "bits/stdc++.h"
using namespace std;

class node{
public:
    int colors[4];
    int rangeCount;
    node():colors{0, 0, 0, 0}{
        rangeCount = 0;
    }

    void putColorInLeaf(int color){
        colors[color]=1;
    }

    int calculateGreen(){
        return max(0, min(colors[0], colors[1]) - colors[2]);
    }

    void setGreen(){
        colors[3] = calculateGreen();
    }

    void removeRed(){
        colors[2] = 0;
    }

    void setGreen(node* left, node* right){
        bool adding = 1;
        for(int i=0; i<3; i++){
            if(left->colors[i] + right->colors[i] != colors[i]){
                adding = 0;
                break;
            }
        }
        if(!adding){
            setGreen();
        }
        else{
            colors[3] = left->colors[3] + right->colors[3];
        }
        int test=0;
    }

    int getColorCount(int color){
        return colors[color];
    }

    void sumColorCount(int color, int leftV, int rightV){
        colors[color]=max(colors[color], leftV+rightV);
    }

    
};

namespace tree{
    #define M 1048576
    node array[2*M];
    int treeSize, size;

    int getFirstNotSmallerPowerOfTwo(int n){
        int result = 1;
        while(n > result){
            result *= 2;
        }
        return result;
    }

    void init(int n){
        size = n;
        treeSize = getFirstNotSmallerPowerOfTwo(n);
        for(int i=0; i<size; i++){
            array[i+treeSize].rangeCount = 1;
        }
        for(int i=size; i<treeSize; i++){
            array[i+treeSize].rangeCount = 0;
        }
        
        int depth = 2;
        while(treeSize/depth){
            for(int i=0; i<treeSize/depth; i++){
                array[i+treeSize/depth].rangeCount = array[(i+treeSize/depth)*2].rangeCount + array[(i+treeSize/depth)*2+1].rangeCount;
            }
            depth *= 2;
        }
    }

    int calculateGreen(){
        for(int i=0; i<size; i++){
            array[i+treeSize].setGreen();
        }

        int depth = 2;
        while(treeSize/depth){
            for(int i=0; i<treeSize/depth; i++){
                node* first = &array[(i+treeSize/depth)*2], *second = &array[(i+treeSize/depth)*2+1];
                array[i+treeSize/depth].setGreen(first, second);
            }
            depth *= 2;
        }
        return array[1].getColorCount(3);
    }

    void insert(int a, int b, int val){
        int left = treeSize + a, right = treeSize + b;
        array[left].putColorInLeaf(val);
        array[right].putColorInLeaf(val);

        while(left/2){
            if(left/2 == right/2 && left != right){ // schodza sie sciezki
                array[left/2].sumColorCount(val, array[left].getColorCount(val), array[right].getColorCount(val));
            } else if(left/2 == right/2 && left == right){ //juz sie zeszly
                if(left % 2 == 0){
                    array[left/2].sumColorCount(val, array[left].getColorCount(val), array[left+1].getColorCount(val));
                } else {
                    array[left/2].sumColorCount(val, array[left].getColorCount(val), array[left-1].getColorCount(val));
                }
            } else if(left/2 != right/2){
                if(left % 2 == 0){
                    array[left/2].sumColorCount(val, array[left].getColorCount(val), array[left+1].rangeCount);
                    array[left+1].colors[val] = array[left+1].rangeCount;
                } else {
                    array[left/2].sumColorCount(val, array[left].getColorCount(val), array[left-1].getColorCount(val));
                }
                if(right % 2 == 1){
                    array[right/2].sumColorCount(val, array[right].getColorCount(val), array[right-1].rangeCount);
                    array[right-1].colors[val] = array[right-1].rangeCount;
                } else {
                    array[right/2].sumColorCount(val, array[right].getColorCount(val), array[right+1].getColorCount(val));
                }
            }
            left /= 2;
            right /= 2;
        }
	}
}

int main(){	
    int n,m; cin >> n >> m;

    tree::init(n);
    while(m--){
        int l, r, k; cin >> l >> r >> k;
        tree::insert(l-1, r-1, k-1);
    }
    int debug = 0;
    cout << tree::calculateGreen();
    debug = 0;
}