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#include <iostream>
#include <vector>
#include <algorithm>

int n, m;
struct Op
{
	bool start;
	int pos;
	int col;
};
std::vector<Op> ops;

int main()
{
    std::cin >> n >> m;
	ops.reserve(m*2);
	for(int i=0;i<m;++i)
	{
		int l,r,k;
		std::cin >> l >> r >> k;
		ops.push_back({true,l-1,k});
		ops.push_back({false,r,k});
	}
	std::sort(ops.begin(),ops.end(),[](const Op& a, const Op& b){ return a.pos<b.pos||(a.pos==b.pos&&!a.start&&b.start);});
	int res=0;
	int col[3]={0};
	int pos=0;
	int i=0;
	while(i<ops.size())
	{
		int new_pos=ops[i].pos;
		if(col[0]&&col[1]&&!col[2])
			res+=new_pos-pos;
		while(i<ops.size()&&ops[i].pos==new_pos)
		{
			col[ops[i].col-1]+=ops[i].start?1:-1;
			++i;
		}
		pos=new_pos;
	}
	std::cout << res;
	return 0;
}