#include <bits/stdc++.h>
using namespace std;

#define NDEBUG
#include <cassert>


typedef long long ll;
typedef long double Double;
typedef unsigned long long ull;
typedef pair<int, int> ii;
typedef pair<ll, ll> llll;
typedef pair<double, double> dd;

typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<llll> vllll;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<long double> vD;

#define sz(a) int((a).size())
#define pb push_back
#define eb emplace_back
#define FOR(var, from, to) for (int var = (from); var <= (to); ++var)
#define rep(var, n) for (int var = 0; var < (n); ++var)
#define rep1(var, n) for (int var = 1; var <= (n); ++var)
#define repC2(vari, varj, n)               \
  for (int vari = 0; vari < (n)-1; ++vari) \
    for (int varj = vari + 1; varj < (n); ++varj)
#define repC3(vari, varj, vark, n)                  \
  for (int vari = 0; vari < (n)-2; ++vari)          \
    for (int varj = vari + 1; varj < (n)-1; ++varj) \
      for (int vark = varj + 1; vark < (n); ++vark)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define tr(i, c) for (auto i = (c).begin(); i != (c).end(); ++i)
#define found(s, e) ((s).find(e) != (s).end())
#define mset(arr, val) memset(arr, val, sizeof(arr))
#define mid(x, y) ((x) + ((y) - (x)) / 2)
#define IN(x, a, b) ((a) <= (x) && (x) <= (b))
#define cons make_pair
#define clamp(v, lo, hi) min(max(v, lo), hi)
#define ABS(x) max((x), -(x))
#define PQ(T) priority_queue<T, vector<T>, greater<T>>

template <typename T1, typename T2>
inline void amin(T1& a, T2 const& b) {
  if (a > b) a = b;
}
template <typename T1, typename T2>
inline void amax(T1& a, T2 const& b) {
  if (a < b) a = b;
}
template <typename X, typename T>
auto vectors(X x, T a) {
  return vector<T>(x, a);
}
template <typename X, typename Y, typename Z, typename... Zs>
auto vectors(X x, Y y, Z z, Zs... zs) {
  auto cont = vectors(y, z, zs...);
  return vector<decltype(cont)>(x, cont);
}

inline ll square(ll x) { return x * x; }
inline ll gcd(ll a, ll b) {
  while (a) swap(a, b %= a);
  return b;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <typename T>
inline T mod(T a, T b) {
  return ((a % b) + b) % b;
}

template <typename T>
int find_left(vector<T>& v, T elem) {
  return (int)(upper_bound(v.begin(), v.end(), elem) - v.begin()) - 1;
}
template <typename T>
int find_right(vector<T>& v, T elem) {
  return (int)(lower_bound(v.begin(), v.end(), elem) - v.begin());
}

const ll MOD = 1000000007LL;

inline ll ADD(ll x, ll y) { return (x + y) % MOD; }
inline ll SUB(ll x, ll y) { return (x - y + MOD) % MOD; }
inline ll MUL(ll x, ll y) { return x * y % MOD; }
inline ll POW(ll x, ll e) {
  ll v = 1;
  for (; e; x = MUL(x, x), e >>= 1)
    if (e & 1) v = MUL(v, x);
  return v;
}
inline ll INV(ll y) { /*assert(y%MOD!=0);*/
  return POW(y, MOD - 2);
}
inline ll DIV(ll x, ll y) { return MUL(x, INV(y)); }

#define INTSPACE 12
char _buf[INTSPACE * 1000000 + 3];

int loadint() {
  if (fgets(_buf, INTSPACE + 3, stdin) == NULL) return 0;
  return atoi(_buf);
}

int loadvec(vector<int>& v, int N = -1) {
  if (N == 0) {
    v.clear();
    return 0;
  }
  if (N == -1) {
    N = loadint();
    if (N == 0) return 0;
  }
  int bufsize = INTSPACE * N + 3;
  if (fgets(_buf, bufsize, stdin) == NULL) return 0;
  v.resize(N);

  int i = 0;
  bool last = false;
  for (char* p = &_buf[0];;) {
    char* q = p;
    while (*q > ' ') ++q;
    if (*q == 0x0D || *q == 0x0A) last = true;
    *q = 0;
    v[i++] = atoi(p);
    if (last || i == N) break;
    p = q + 1;
  }
  return i;
}
void read_cr() { fgets(_buf, 256, stdin); }

void horizontal(vector<int>& v) {
  int L = v.size();
  for (int i = 0; i < L; ++i) {
    printf("%d%c", v[i], (i == L - 1) ? '\n' : ' ');
  }
}
void horizontall(vector<long long>& v) {
  int L = v.size();
  for (int i = 0; i < L; ++i) {
    printf("%lld%c", v[i], (i == L - 1) ? '\n' : ' ');
  }
}

class UnionFind2D {
 public:
  vector<int> data;
  int height, width;
  int count;
  inline int RC(int r, int c) { return r * width + c; }
  inline bool inside(int r, int c) { return (0 <= r && r < height && 0 <= c && c < width); }

 public:
  UnionFind2D(int height, int width)
      : data(height * width, -1), height(height), width(width), count(height * width) {}

  bool unionSet(int x, int y) {
    x = root(x);
    y = root(y);
    if (x != y) {
      if (data[y] < data[x]) swap(x, y);
      data[x] += data[y];
      data[y] = x;
      --count;
    }
    return x != y;
  }
  bool isSame(int x, int y) { return root(x) == root(y); }
  int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
  int size(int x) { return -data[root(x)]; }

  bool unionSet(int r0, int c0, int r1, int c1) {
    if (!inside(r0, c0) || !inside(r1, c1)) return false;
    return unionSet(RC(r0, c0), RC(r1, c1));
  }
  bool isSame(int r0, int c0, int r1, int c1) {
    if (!inside(r0, c0) || !inside(r1, c1)) return false;
    return root(r0, c0) == root(r1, c1);
  }
  int root(int r, int c) {
    if (!inside(r, c)) return -1;
    return root(RC(r, c));
  }
  int size(int r, int c) {
    if (!inside(r, c)) return 0;
    return size(RC(r, c));
  }

  bool unionSet(pair<int, int>& p0, pair<int, int>& p1) {
    return unionSet(p0.first, p0.second, p1.first, p1.second);
  }
  bool isSame(pair<int, int>& p0, pair<int, int>& p1) {
    return isSame(p0.first, p0.second, p1.first, p1.second);
  }
  int root(pair<int, int>& p) { return root(p.first, p.second); }
  int size(pair<int, int>& p) { return size(p.first, p.second); }
};

#define HW(x, y) (W * (x) + (y))
#define HW_X(z) ((z) / W)
#define HW_Y(z) ((z) % W)

int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
int solve(int H, int W, int K, int x1, int y1, int x2, int y2, vs& c) {
  {
    UnionFind2D uf(H, W);
    rep(x, H) rep(y, W) {
      if (c[x][y] == '@') continue;
      rep(i, 4) {
        if (x + 1 < H) {
          uf.unionSet(x, y, x + 1, y);
        }
        if (y + 1 < W) {
          uf.unionSet(x, y, x, y + 1);
        }
      }
    }
    if (uf.root(x1, y1) != uf.root(x2, y2)) return -1;
  }

  vvi d(H, vi(W, INT_MAX));
  vvi dq(H, vi(W, INT_MAX));

  ;
  queue<int> q;
  q.emplace(HW(x1, y1));
  dq[x1][y1] = 0;

  while (!q.empty()) {
    int z = q.front();
    q.pop();
    int x = HW_X(z), y = HW_Y(z);
    int dp = dq[x][y];
    assert(c[x][y] != '@');

    if (d[x][y] != INT_MAX) continue;
    d[x][y] = dp;


    for (int xi = x - 1, T = max(x - K, 0); xi >= T; --xi) {
      if (c[xi][y] == '@') break;
      if (d[xi][y] != INT_MAX) break;

      if (dq[xi][y] == INT_MAX) {
        q.emplace(HW(xi, y));
        dq[xi][y] = dp + 1;
      }
    }
    for (int xi = x + 1, T = min(x + K, H - 1); xi <= T; ++xi) {
      if (c[xi][y] == '@') break;
      if (d[xi][y] != INT_MAX) break;

      if (dq[xi][y] == INT_MAX) {
        q.emplace(HW(xi, y));
        dq[xi][y] = dp + 1;
      }
    }
    for (int yi = y - 1, T = max(y - K, 0); yi >= T; --yi) {
      if (c[x][yi] == '@') break;
      if (d[x][yi] != INT_MAX) break;

      if (dq[x][yi] == INT_MAX) {
        q.emplace(HW(x, yi));
        dq[x][yi] = dp + 1;
      }
    }
    for (int yi = y + 1, T = min(y + K, W - 1); yi <= T; ++yi) {
      if (c[x][yi] == '@') break;
      if (d[x][yi] != INT_MAX) break;

      if (dq[x][yi] == INT_MAX) {
        q.emplace(HW(x, yi));
        dq[x][yi] = dp + 1;
      }
    }
  }


  return (d[x2][y2] == INT_MAX) ? -1 : d[x2][y2];
}

int main() {
  ios_base::sync_with_stdio(
      false);
  cin.tie(NULL);
  int H, W, K;
  cin >> H >> W >> K;
  int x1, y1, x2, y2;
  cin >> x1 >> y1 >> x2 >> y2;
  --x1;
  --y1;
  --x2;
  --y2;
  vs c(H);
  rep(i, H) cin >> c[i];
  cout << solve(H, W, K, x1, y1, x2, y2, c) << endl;
  return 0;
}


Measured memory_bytes: 15748