#include <algorithm>
#include <cstdio>
#include <cstring>
#define FILEIO(filename) (freopen(filename ".in", "r", stdin), freopen(filename ".out", "w", stdout))
typedef long long ll;
typedef unsigned long long ull;
const int N = 6000005;
const int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, -1, 0, 1};
int r, c, n;
char s[N];
int col[N];
inline bool inmap(int x, int y)
{
    return x >= 0 && x < r && y >= 0 && y < c;
}
inline int getid(int x, int y)
{
    return x * c + y;
}
inline void getpos(int id, int &x, int &y)
{
    x = id / c, y = id % c;
    return;
}
inline bool reach(int x1, int y1, int x2, int y2)
{
    int v1 = std::abs(x1 - x2), v2 = std::abs(y1 - y2);
    return v1 <= n && v2 <= n && (v1 < n || v2 < n);
}
inline bool reachid(int id1, int id2)
{
    int x1, y1, x2, y2;
    getpos(id1, x1, y1), getpos(id2, x2, y2);
    return reach(x1, y1, x2, y2);
}
int st, ed;
struct DSU
{
    int fa[N], siz[N], mx[N];
    inline void init(int l)
    {
        for (int i = 0; i < l; ++i)
            fa[i] = i, siz[i] = 1, mx[i] = i;
        return;
    }
    int find(int x)
    {
        return fa[x] == x ? x : fa[x] = find(fa[x]);
    }
    inline void merge(int x, int y)
    {
        x = find(x), y = find(y);
        if(x == y)
            return;
        if(siz[x] > siz[y])
            std::swap(x, y);
        fa[x] = y, mx[y] = std::max(mx[x], mx[y]);
        return;
    }
    inline int get(int x)
    {
        return mx[find(x)];
    }
} Dr, Dc;
inline void del(int id)
{
    int x, y;
    getpos(id, x, y);
    Dr.merge(id, y == c - 1 ? r * c : id + 1);
    Dc.merge(id, x == r - 1 ? r * c : id + c);
    return;
}
int dis[N];
int stk[N], top;
int tmp[N], ttop;
int main(void)
{
    scanf("%d%d%d", &r, &c, &n);
    {
        int x, y;
        scanf("%d%d", &x, &y);
        st = getid(x - 1, y - 1);
        scanf("%d%d", &x, &y);
        ed = getid(x - 1, y - 1);
    }
    for (int i = 0; i < r;++i)
    {
        scanf("%s", s);
        for (int j = 0; j < c;++j)
            col[getid(i, j)] = s[j] == '#';
    }
    Dr.init(r * c + 1), Dc.init(r * c + 1);
    memset(dis, 0x3f, sizeof(dis)), dis[st] = 0;
    stk[++top] = st;
    while(1)
    {
        for (int i = 1;i <= top;++i)
        {
            int id = stk[i], x, y;
            if(id == ed)
                return printf("%d\n", dis[id]), 0;
            getpos(id, x, y);
            del(id);
            for (int o = 0; o < 4; ++o)
            {
                int nx = x + dx[o], ny = y + dy[o];
                if(!inmap(nx, ny))
                    continue;
                int yid = getid(nx, ny);
                if(!col[yid] && dis[yid] > dis[id])
                    dis[yid] = dis[id], stk[++top] = yid;
            }
        }
        memcpy(tmp, stk, sizeof(int) * (top + 5)), ttop = top, top = 0;
        for (int i = 1; i <= ttop;++i)
        {
            int id = tmp[i], x, y;
            if(reachid(id, ed))
                return printf("%d\n", dis[id] + 1), 0;
            getpos(id, x, y);
            int rl = std::max(0, x - n), rr = std::min(r - 1, x + n);
            int cl = std::max(0, y - n), cr = std::min(c - 1, y + n);
            int sp = 0, ep = 0;
            sp = getid(rl, cl + (!reach(rl, cl, x, y))), ep = getid(rl, cr - (!reach(rl, cr, x, y)));
            for (int u = Dr.find(sp); u <= ep;u = Dr.get(u))
                if (dis[u] > dis[id] + 1)
                    dis[stk[++top] = u] = dis[id] + 1, del(u);
            sp = getid(rr, cl + (!reach(rr, cl, x, y))), ep = getid(rr, cr - (!reach(rr, cr, x, y)));
            for (int u = Dr.find(sp); u <= ep; u = Dr.get(u))
                if (dis[u] > dis[id] + 1)
                    dis[stk[++top] = u] = dis[id] + 1, del(u);
            sp = getid(rl + (!reach(rl, cl, x, y)), cl), ep = getid(rr - (!reach(rr, cl, x, y)), cl);
            for (int u = Dc.find(sp); u <= ep; u = Dc.get(u))
                if (dis[u] > dis[id] + 1)
                    dis[stk[++top] = u] = dis[id] + 1, del(u);
            sp = getid(rl + (!reach(rl, cr, x, y)), cr), ep = getid(rr - (!reach(rr, cr, x, y)), cr);
            for (int u = Dc.find(sp); u <= ep; u = Dc.get(u))
                if (dis[u] > dis[id] + 1)
                    dis[stk[++top] = u] = dis[id] + 1, del(u);
        }
    }
    puts("-1");
    return 0;
}