#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define mp make_pair
using namespace std;
auto IN = freopen("plusminus.in", "r", stdin);
auto OUT = freopen("plusminus.out", "w", stdout);
auto mread = [](){int x;scanf("%lld", &x);return x;};
const int N = 1e6 + 5, MOD = 998244353;
int n = mread(), m = mread(), k = mread(), e;
vector<pair<int, int> > v[N];
int ksm(int x, int k){
    int ans = 1, now = x;
    while(k){
        if(k & 1){
            ans = ans * now % MOD;
        }
        now = now * now % MOD;
        k >>= 1;
    }
    return ans;
}
signed main(){
    if((n & 1) + (m & 1) == 1){
        printf("0");
        return 0;
    }
    if(n < m){
        e = 1;
        swap(n, m);
    }
    for(int i = 1, x, y, z; i <= k; i ++){
        cin >> x >> y >> z;
        if(e){
            swap(x, y);
        }
        v[x].push_back(mp(y, z));
    }
    int ans = 1;
    for(int i = 1; i <= n; i ++){
        if(v[i].size() < m){
            ans = ans * ksm(2, m - v[i].size() - 1) % MOD;
        }
        else{
            int tmp = 1;
            for(auto t : v[i]){
                tmp *= t.se;
            }
            if(tmp == 1){
                ans = 0;
            }
        }
    }
    printf("%lld\n", ans * ksm(ksm(2, m - 1), MOD - 2) % MOD);
    return 0;
}