import std.stdio, std.string, std.conv, std.range;
import std.algorithm, std.array, std.typecons, std.container;
import std.math, std.numeric, std.random, core.bitop;

enum inf = 1_001_001_001;
enum infl = 1_001_001_001_001_001_001L;

enum mod = 1_000_000_007L;




void main() {
    int W, H, N;
    scan(W, H, N);
    int l = 0, r = W;
    int d = 0, u = H;
    foreach (i ; 0 .. N) {
        int xi, yi, ai;
        scan(xi, yi, ai);
        if (ai == 1) {
            chmax(l, xi);
        }
        else if (ai == 2) {
            chmin(r, xi);
        }
        else if (ai == 3) {
            chmax(d, yi);
        }
        else {
            chmin(u, yi);
        }

        debug {
            writefln("%s, %s", l, r);
            writefln("%s, %s", d, u);
        }
    }

    auto ans = max(0, r - l) * max(0, u - d);
    writeln(ans);
}




void scan(T...)(ref T args) {
    auto line = readln.split;
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront;
    }
    assert(line.empty);
}

void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}

bool chmin(T, U...)(ref T x, U args) {
    bool isChanged;
    foreach (arg; args) if (x > arg) {
        x = arg;
        isChanged = true;
    }
    return isChanged;
}

bool chmax(T, U...)(ref T x, U args) {
    bool isChanged;
    foreach (arg; args) if (x < arg) {
        x = arg;
        isChanged = true;
    }
    return isChanged;
}

void yes(bool ok, string y = "Yes", string n = "No") {
    return writeln(ok ? y : n);
}
