#include <bits/stdc++.h>

using namespace std;

string s[1005];
int a[1005][1005];

int xs[4] = { 0 , +1 , 0 , -1 };
int ys[4] = { +1 , 0 , -1 , 0 };

int main()
{
    int n,m,k;
    cin>>n>>m>>k;

    for (int i=1 ; i<=n ; i++)
    {    cin>>s[i]; s[i] = "#"+s[i]+"#"; }

    for (int i=0 ; i<m+1 ; i++) s[0].push_back('#') , s[n+1].push_back('#');

    int ans = 0;
    queue<pair<int,int>> q;

    for (int i=0 ;i<k ; i++)
    {
        int x,y; cin>>x>>y;
        s[x][y] = '#';
        q.push( make_pair( x,y ) );
    }

    while ( q.empty() == false )
    {
        pair<int,int> p = q.front() ; q.pop();

        for (int i=0 ; i<4 ; i++)
        {
            int x = p.first + xs[i] , y = p.second + ys[i];
            if ( s[x][y] != '#' )
            {
                a[x][y] = a[p.first][p.second] + 1;
                s[x][y] = '#';
                ans += a[x][y];
                q.push( make_pair( x , y ) );
            }
        }
    }

    cout<<ans<<"\n";
}