#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);
vector<string> split(const string &);

/*
 * Complete the 'gridlandMetro' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts following parameters:
 *  1. INTEGER n
 *  2. INTEGER m
 *  3. INTEGER k
 *  4. 2D_INTEGER_ARRAY track
 */
vector<vector<long long>> merge(vector<vector<long long>> tracks) {
    sort(tracks.begin(), tracks.end(), [](vector<long long>& a, vector<long long>& b) {
        return a[0] < b[0];
    });

    if (tracks.empty()) {
        return {};
    }

    vector<vector<long long>> merged_tracks;
    merged_tracks.push_back(tracks[0]);

    for (int i = 1; i < tracks.size(); i++) {
        long long last_end = merged_tracks.back()[1];
        long long current_start = tracks[i][0];
        long long current_end = tracks[i][1];

        if (current_start <= last_end + 1) { 
            merged_tracks.back()[1] = max(last_end, current_end);
        } else {
            merged_tracks.push_back(tracks[i]);
        }
    }
    return merged_tracks;
}

long long gridlandMetro(long long n, long long m, int k, vector<vector<int>> track) {

    long long totalsquares = n * m; 
    
    unordered_map<int, vector<vector<long long>>> mp; 

    for (const auto& i : track) {
        mp[i[0]].push_back({(long long)i[1], (long long)i[2]}); 
    }

    for (const auto& pair : mp) {
        const int row_index = pair.first;
        const vector<vector<long long>>& tracks_in_row = pair.second;
        
        vector<vector<long long>> merged_segments = merge(tracks_in_row);
        
        long long covered_cells_in_row = 0;
        
        for (const auto& segment : merged_segments) {
            covered_cells_in_row += segment[1] - segment[0] + 1; 
        }
        
        totalsquares -= covered_cells_in_row;
    }
    
    return totalsquares;
}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string first_multiple_input_temp;
    getline(cin, first_multiple_input_temp);

    vector<string> first_multiple_input = split(rtrim(first_multiple_input_temp));

    int n = stoi(first_multiple_input[0]);

    int m = stoi(first_multiple_input[1]);

    int k = stoi(first_multiple_input[2]);

    vector<vector<int>> track(k);

    for (int i = 0; i < k; i++) {
        track[i].resize(3);

        string track_row_temp_temp;
        getline(cin, track_row_temp_temp);

        vector<string> track_row_temp = split(rtrim(track_row_temp_temp));

        for (int j = 0; j < 3; j++) {
            int track_row_item = stoi(track_row_temp[j]);

            track[i][j] = track_row_item;
        }
    }

    long long result = gridlandMetro(n, m, k, track);

    fout << result << "\n";

    fout.close();

    return 0;
}

string ltrim(const string &str) {
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str) {
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

vector<string> split(const string &str) {
    vector<string> tokens;

    string::size_type start = 0;
    string::size_type end = 0;

    while ((end = str.find(" ", start)) != string::npos) {
        tokens.push_back(str.substr(start, end - start));

        start = end + 1;
    }

    tokens.push_back(str.substr(start));
		

    return tokens;
}