#include <iostream>
#include <algorithm>

typedef long long ll;
typedef double lf;

// #define DEBUG 1
struct IO
{
    #define MAXSIZE (1 << 20)
    #define isdigit(x) (x >= '0' && x <= '9')
    char buf[MAXSIZE], *p1, *p2;
    char pbuf[MAXSIZE], *pp;
    #if DEBUG
    #else
    IO() : p1(buf), p2(buf), pp(pbuf) {}
    ~IO() {fwrite(pbuf, 1, pp - pbuf, stdout);}
    #endif
    #define gc() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, MAXSIZE, stdin), p1 == p2) ? ' ' : *p1++)
    #define blank(x) (x == ' ' || x == '\n' || x == '\r' || x == '\t')

    template <typename T>
    void Read(T &x)
    {
        #if DEBUG
        std::cin >> x;
        #else
        bool sign = 0; char ch = gc(); x = 0;
        for (; !isdigit(ch); ch = gc())
            if (ch == '-') sign = 1;
        for (; isdigit(ch); ch = gc()) x = x * 10 + (ch ^ 48);
        if (sign) x = -x;
        #endif
    }
    void Read(char *s)
    {
        #if DEBUG
        std::cin >> s;
        #else
        char ch = gc();
        for (; blank(ch); ch = gc());
        for (; !blank(ch); ch = gc()) *s++ = ch;
        *s = 0;
        #endif
    }
    void Read(char &c) {for (c = gc(); blank(c); c = gc());}

    void Push(const char &c)
    {
        #if DEBUG
        putchar(c);
        #else
        if (pp - pbuf == MAXSIZE) fwrite(pbuf, 1, MAXSIZE, stdout), pp = pbuf;
        *pp++ = c;
        #endif
    }
    template <typename T>
    void Write(T x)
    {
        if (x < 0) x = -x, Push('-');
        static T sta[35];
        int top = 0;
        do sta[top++] = x % 10, x /= 10; while (x);
        while (top) Push(sta[--top] ^ 48);
    }
    template <typename T>
    void Write(T x, char lst) {Write(x), Push(lst);}
} IO;
#define Read(x) IO.Read(x)
#define Write(x, y) IO.Write(x, y)
#define Put(x) IO.Push(x)

using namespace std;

const int MAXN = 1e5 + 10;

int n, m, t;

struct Data
{
    int l, r;
    bool operator < (const Data u) const {return l < u.l;}
};
vector <Data> a[MAXN << 1], b;

int main()
{
    #if DEBUG
    #else
    ios::sync_with_stdio(0), cin.tie(0);
    #endif
    Read(n), Read(m), Read(t);
    if (m > 2 * t + 1) {cout << "NO\n"; return 0;}
    for (int i = 1, l, r, x; i <= t; i++) Read(l), Read(r), Read(x), a[x].push_back(Data{l, r});
    ll sum1 = 0, sum2 = 0;
    for (int i = 1; i <= m; i++)
    {
        sort(a[i].begin(), a[i].end());
        if (!a[i].size()) {sum1 += n, sum2 += n - 1; continue;}
        int pre = a[i][0].l, nxt = a[i][0].r; ll cur1 = n, cur2 = n - 1;
        for (int j = 0; j < a[i].size(); j++)
        {
            if (a[i][j].l <= nxt) nxt = max(nxt, a[i][j].r);
            else
            {
                cur1 -= nxt - pre + 1, cur2 -= nxt - pre + (pre != 1) + (nxt != n);
                pre = a[i][j].l, nxt = a[i][j].r;
            }
        }
        cur1 -= nxt - pre + 1, cur2 -= nxt - pre + (pre != 1) + (nxt != n);
        sum1 += cur1, sum2 += cur2;
    }
    // cout << sum1 << " " << sum2 << "\n";
    for (int i = 2; i <= m; i++)
    {
        b.clear();
        for (auto x : a[i - 1]) b.push_back(x);
        for (auto x : a[i]) b.push_back(x);
        sort(b.begin(), b.end());
        if (!b.size()) {sum2 += n; continue;}
        int pre = b[0].l, nxt = b[0].r; ll cur = n;
        for (int j = 0; j < b.size(); j++)
        {
            // cout << b[j].l << " " << b[j].r << "\n";
            if (b[j].l <= nxt) nxt = max(nxt, b[j].r);
            else
            {
                cur -= nxt - pre + 1;
                pre = b[j].l, nxt = b[j].r;
            }
        }
        cur -= nxt - pre + 1;
        sum2 += cur;
    }
    // cout << sum1 << " " << sum2 << "\n";
    if (sum1 == sum2 + 1) cout << "YES\n";
    else cout << "NO\n";
    return 0;
}

answer.code:84:1: error: ‘vector’ does not name a type
   84 | vector <Data> a[MAXN << 1], b;
      | ^~~~~~
answer.code: In function ‘int main()’:
answer.code:94:70: error: ‘a’ was not declared in this scope
   94 |     for (int i = 1, l, r, x; i <= t; i++) Read(l), Read(r), Read(x), a[x].push_back(Data{l, r});
      |                                                                      ^
answer.code:98:14: error: ‘a’ was not declared in this scope
   98 |         sort(a[i].begin(), a[i].end());
      |              ^
answer.code:103:30: error: ‘nxt’ was not declared in this scope
  103 |             if (a[i][j].l <= nxt) nxt = max(nxt, a[i][j].r);
      |                              ^~~
answer.code:110:17: error: ‘nxt’ was not declared in this scope
  110 |         cur1 -= nxt - pre + 1, cur2 -= nxt - pre + (pre != 1) + (nxt != n);
      |                 ^~~
answer.code:116:9: error: ‘b’ was not declared in this scope
  116 |         b.clear();
      |         ^
answer.code:117:23: error: ‘a’ was not declared in this scope
  117 |         for (auto x : a[i - 1]) b.push_back(x);
      |                       ^
answer.code:118:23: error: ‘a’ was not declared in this scope
  118 |         for (auto x : a[i]) b.push_back(x);
      |                       ^
answer.code:125:27: error: ‘nxt’ was not declared in this scope
  125 |             if (b[j].l <= nxt) nxt = max(nxt, b[j].r);
      |                           ^~~
answer.code:132:16: error: ‘nxt’ was not declared in this scope
  132 |         cur -= nxt - pre + 1;
      |                ^~~