import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    static final int MOD = 998244353;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int h = sc.nextInt();
        int w = sc.nextInt();
        int k = sc.nextInt();
        long ans = 0;
        while (k-- > 0) {
            int r = sc.nextInt();
            int c = sc.nextInt();
            int v = sc.nextInt();
            long current = (long)r * w;
            current += MOD - getValue(w - c, r);
            current %= MOD;
            current += MOD - getValue(c - 1, r);
            current %= MOD;
            ans += current * v % MOD;
            ans %= MOD;
        }
        System.out.println(ans);
    }
    
    static long getValue(long width, long height) {
        return (width + Math.max(width - height + 1, 1)) * Math.min(height, width) / 2 % MOD;
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}