记住一定要区分n和m分别代表什么，我已经因为这个两道题浪费很多时间了
然后这个道题有点类似最长上升子序列n平方的做法，只是判断的条件不同而已
#include<cstdio>
#include<algorithm>
#include<cmath>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
using namespace std;const int MAXN = 11234;
int f[MAXN], n, m;
struct node
{int t, x, y;void read() { scanf("%d%d%d", &t, &x, &y); }bool operator < (const node& rhs) const{return t < rhs.t; }
}a[MAXN];bool judge(int i, int j)
{return (a[j].t - a[i].t) >= abs(a[i].x - a[j].x) + abs(a[i].y - a[j].y);
}int main()
{scanf("%d%d", &n, &m);REP(i, 0, m) a[i].read();sort(a, a + m);int ans = 1;f[0] = 1;REP(i, 1, m){f[i] = 1;REP(j, 0, i)if(judge(j, i))f[i] = max(f[i], f[j] + 1);ans = max(ans, f[i]);}printf("%d\n", ans);return 0;
}