#include <bits/stdc++.h>

#define fastio ios_base::sync_with_stdio(0); cin.tie(0)

using namespace std;

using ll = long long;

#define int ll
#define pb push_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()

void dbg_out() { cerr << endl; }
template <typename H, typename... T>
void dbg_out(H h, T... t) { cerr << ' ' << h; dbg_out(t...); }
#define dbg(...) { cerr << #__VA_ARGS__ << ':'; dbg_out(__VA_ARGS__); }

int imove[] = {-1, +1, 0, 0},
	jmove[] = {0, 0, -1, +1};

const int INF = 1e18;

signed main() {
	fastio;
	int n, m, k; cin>>n>>m>>k;
	
	pair<int,int> st;
	vector<vector<int>> val(n, vector<int>(m));
	for (int i = 1; i <= k; i++) {
		int x, y; cin>>x>>y; x--, y--;
		val[x][y] = k - i;
		if (i == 1) st = {x, y};
	}

	vector<string> grid(n);
	for (int i = 0; i < n; i++) {
		cin>>grid[i];
	}

	auto valid = [&](int i, int j) {
		return (0 <= i and i < n and 0 <= j and j < m and grid[i][j] == '.');
	};

	vector<vector<int>> dist(n, vector<int>(m, INF));
	
	priority_queue<array<int,3>> pq;
	queue<array<int,3>> q;
	q.push({0, st.first, st.second});
	dist[st.first][st.second] = 0;
	while (q.size()) {
		auto [d, i, j] = q.front();
		q.pop();

		while (pq.size() and pq.top()[0] == -d) {
			auto [cur_dist, ii, jj] = pq.top();
			if (-cur_dist == dist[ii][jj]) {
				q.push({-cur_dist, ii, jj});
			}
			pq.pop();
		}

		for (int k = 0; k < 4; k++) {
			int ii = i+imove[k],
				jj = j+jmove[k];

			if (valid(ii, jj)) {
				int t = max(0LL, val[ii][jj] - d) + d + 1;
				if (dist[ii][jj] > t) {
					dist[ii][jj] = t;
					if (t == d+1) {
						q.push({t, ii, jj});
					} else {
						pq.push({-t, ii, jj});
					}
				}
			}
		}
	}

	unsigned long long res = 0;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < m; j++) {
			if (dist[i][j] != INF) {
				res += dist[i][j]*dist[i][j];
			}
		}
	}
	cout<<res<<'\n';

	return 0;
}