#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MXN = 2000;
using pii = pair<int,int>;
char A[MXN][MXN];
signed main() {
    cin.tie(0)->sync_with_stdio(0);
    int n, m, k; cin >> n >> m >> k;
    vector<pii> Q;
    for(int i=0;i<2000-1;i++){
        for(int j=0;j<2000-1;j++) A[i][j] = '.';
    }
    for(int i=1000;i<1000+n;i++){
        for(int j=1000;j<1000+m;j++){
            cin >> A[i][j];
            if(A[i][j]=='#')
            Q.push_back({i,j});
        }
    }
    for(int d=0;d<min(k,100LL);d++){
        vector<pii> nq;
        for(auto &[x,y] : Q) {
            for(int dx=-1;dx<2;dx++) for(int dy=-1;dy<2;dy++){
                int ax = x+dx, ay = y+dy;
                if(A[ax][ay]=='.') {
                    A[ax][ay] = '#';
                    nq.push_back({ax,ay});
                }
            }
        }
        swap(Q,nq);
    }
    k = max(0LL,k-100);
    int ans = 0;
    for(int i=0;i<2000;i++) for(int j=0;j<2000;j++)
        ans += (A[i][j]=='#');
    if(k) {
        int x=-1, y=-1;
        for(int i=0;i<2000;i++) {
            for(int j=0;j<2000;j++) if(A[i][j]=='#'){
                x=i,y=j;
                break;
            }
            if(x!=-1) break;
        }
        if(x==-1 && y==-1) {
            cout << 0;
            return 0;
        }
        int ex = x, ey = y;
        while(A[ex][y]=='#') ex++;
        while(A[x][ey]=='#') ey++;
        int lx = ex-x, ly = ey-y;
        lx += 2*k, ly += 2*k;
        
        cout << lx*ly;
    }
    else {
        cout << ans;
    }
}