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#include <bits/stdc++.h>
using namespace std;
#define fastIO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define fi first
#define se second
#define all(x) begin(x), end(x)
#define repeat(i, x) for (int i = 0; i < (x); ++i)

pair<int, int> op[int(2e6)+2];

int main()
{
    fastIO;

    int ans = 0;
    int curr = 1;
    int l, r, k;
    
    int n, m;
    cin >> n >> m;
    
    repeat(i, m)
    {
    	cin >> l >> r >> k;
    	
    	op[2*i].fi = l;
    	op[2*i].se = k;
    	op[2*i+1].fi = r+1;
    	op[2*i+1].se = -k;
    }
    
    sort(op, op + 2 * m);
    
    int cols[3] = {0,0,0};
    
    for (int i = 0; i < 2 * m; ++i)
    {
    	if (cols[0] && cols[1] && !cols[2])
    		ans += op[i].fi - curr;
    	curr = op[i].fi;
    	
    	cols[abs(op[i].se) - 1] += (op[i].se > 0 ? 1 : -1);
    }
    
    cout << ans;

    return 0;
}