#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 110000;
const int mod = 1e9 + 7; 
int t, n, m, v, ans;
struct node {
	int c, d;
}a[N];
bool cmp(node x, node y) {
	return x.c != y.c ? x.c < y.c : x.d < y.d;
}
inline int P(int x, int y) {
	int ans = 1;
	while (y) {
		if (y & 1) ans = ans * x % mod;
		x = x * x % mod;
		y >>= 1;
	}
	return ans;
}
signed main() {
	scanf("%lld", &t);
	while (t--) {
		ans = 0;
		scanf("%lld%lld%lld", &n, &m, &v);
		for (int i = 1; i <= m; i++) {
			scanf("%lld%lld", &a[i].c, &a[i].d);
		}
		sort(a + 1, a + m + 1, cmp);
		int flag = 0;
		for (int i = 1; i < m; i++) {
			if (a[i].c == a[i + 1].c && a[i].d != a[i + 1].d) {
				flag = 1;
				break;
			}
		}
		if (flag) {
			printf("0\n");
			continue;
		}
		ans = P(v, 2 * a[1].c - 2);
		for (int i = 1; i < m; i++) {
			if (a[i].c == a[i + 1].c) continue;
			int l = a[i + 1].c - a[i].c;
			ans = ans * ((P(v, 2 * l) - P(v, l - 1) * (v - 1) % mod) % mod + mod) % mod;
		}
		ans = ans * P(v, 2 * n - 2 * a[m].c);
		printf("%lld\n", ans % mod);
	}
	return 0;
}

看这一行：ans = ans * ((P(v, 2 * l) - P(v, l - 1) * (v - 1) % mod) % mod + mod) % mod;，为什么会有一个 $+mod$，怎么会是负数呢？

没有这个就 $65pts$，加上就 AC 了。