import std.stdio;
import std.string;
import std.format;
import std.conv;
import std.typecons;
import std.algorithm;
import std.functional;
import std.bigint;
import std.numeric;
import std.array;
import std.math;
import std.range;
import std.container;
import std.concurrency;
import std.traits;
import std.uni;
import std.regex;
import core.bitop : popcnt;
alias Generator = std.concurrency.Generator;

enum long INF = long.max/5;

void main() {
  long H, W, K;
  scanln(H, W, K);

  struct P {
    long y, x;
  }

  P s, g;
  scanln(s.y, s.x, g.y, g.x);
  s.x--; s.y--;
  g.x--; g.y--;

  bool[][] bss = H.rep!(() => readln.chomp.map!"a=='@'".array);

  long[][] dss = new long[][](H, W);
  foreach(y; 0..H) foreach(x; 0..W) {
    dss[y][x] = INF;
  }
  dss[s.y][s.x] = 0;

  auto list = DList!P(s);
  while(!list.empty) {
    P p = list.front;
    list.removeFront;
    long d = dss[p.y][p.x] + 1;
    {
      // right
      foreach(i; 1..K+1) {
        P q = P(p.y, p.x + i);
        if (q.y < 0 || q.y >= H) break;
        if (q.x < 0 || q.x >= W) break;
        if (bss[q.y][q.x]) break;
        if (d > dss[q.y][q.x]) break;
        if (d < dss[q.y][q.x]) {
          list.insertBack(q);
          dss[q.y][q.x] = d;
        }
      }
    }
    {
      // left
      foreach(i; 1..K+1) {
        P q = P(p.y, p.x - i);
        if (q.y < 0 || q.y >= H) break;
        if (q.x < 0 || q.x >= W) break;
        if (bss[q.y][q.x]) break;
        if (d > dss[q.y][q.x]) break;
        if (d < dss[q.y][q.x]) {
          list.insertBack(q);
          dss[q.y][q.x] = d;
        }
      }
    }
    {
      // down
      foreach(i; 1..K+1) {
        P q = P(p.y + i, p.x);
        if (q.y < 0 || q.y >= H) break;
        if (q.x < 0 || q.x >= W) break;
        if (bss[q.y][q.x]) break;
        if (d > dss[q.y][q.x]) break;
        if (d < dss[q.y][q.x]) {
          list.insertBack(q);
          dss[q.y][q.x] = d;
        }
      }
    }
    {
      // up
      foreach(i; 1..K+1) {
        P q = P(p.y - i, p.x);
        if (q.y < 0 || q.y >= H) break;
        if (q.x < 0 || q.x >= W) break;
        if (bss[q.y][q.x]) break;
        if (d > dss[q.y][q.x]) break;
        if (d < dss[q.y][q.x]) {
          list.insertBack(q);
          dss[q.y][q.x] = d;
        }
      }
    }
  }

  if (dss[g.y][g.x] == INF) {
    writeln(-1);
  } else {
    dss[g.y][g.x].writeln;
  }
}

// ----------------------------------------------


void times(alias fun)(long n) {
  // n.iota.each!(i => fun());
  foreach(i; 0..n) fun();
}
auto rep(alias fun, T = typeof(fun()))(long n) {
  // return n.iota.map!(i => fun()).array;
  T[] res = new T[n];
  foreach(ref e; res) e = fun();
  return res;
}

T ceil(T)(T x, T y) if (isIntegral!T || is(T == BigInt)) {
  // `(x+y-1)/y` will only work for positive numbers ...
  T t = x / y;
  if (y > 0 && t * y < x) t++;
  if (y < 0 && t * y > x) t++;
  return t;
}

T floor(T)(T x, T y) if (isIntegral!T || is(T == BigInt)) {
  T t = x / y;
  if (y > 0 && t * y > x) t--;
  if (y < 0 && t * y < x) t--;
  return t;
}

ref T ch(alias fun, T, S...)(ref T lhs, S rhs) {
  return lhs = fun(lhs, rhs);
}
unittest {
  long x = 1000;
  x.ch!min(2000);
  assert(x == 1000);
  x.ch!min(3, 2, 1);
  assert(x == 1);
  x.ch!max(100).ch!min(1000); // clamp
  assert(x == 100);
  x.ch!max(0).ch!min(10); // clamp
  assert(x == 10);
}

mixin template Constructor() {
  import std.traits : FieldNameTuple;
  this(Args...)(Args args) {
    // static foreach(i, v; args) {
    foreach(i, v; args) {
      mixin("this." ~ FieldNameTuple!(typeof(this))[i]) = v;
    }
  }
}

template scanln(Args...) {
  enum sep = " ";

  enum n = (){
    long n = 0;
    foreach(Arg; Args) {
      static if (is(Arg == class) || is(Arg == struct) || is(Arg == union)) {
        n += Fields!Arg.length;
      } else {
        n++;
      }
    }
    return n;
  }();

  enum fmt = n.rep!(()=>"%s").join(sep);

  enum argsString = (){
    string[] xs = [];
    foreach(i, Arg; Args) {
      static if (is(Arg == class) || is(Arg == struct) || is(Arg == union)) {
        foreach(T; FieldNameTuple!Arg) {
          xs ~= "&args[%d].%s".format(i, T);
        }
      } else {
        xs ~= "&args[%d]".format(i);
      }
    }
    return xs.join(", ");
  }();

  void scanln(auto ref Args args) {
    string line = readln.chomp;
    static if (__VERSION__ >= 2074) {
      mixin(
        "line.formattedRead!fmt(%s);".format(argsString)
      );
    } else {
      mixin(
        "line.formattedRead(fmt, %s);".format(argsString)
      );
    }
  }
}

// fold was added in D 2.071.0
static if (__VERSION__ < 2071) {
  template fold(fun...) if (fun.length >= 1) {
    auto fold(R, S...)(R r, S seed) {
      static if (S.length < 2) {
        return reduce!fun(seed, r);
      } else {
        return reduce!fun(tuple(seed), r);
      }
    }
  }
}

// popcnt with ulongs was added in D 2.071.0
static if (__VERSION__ < 2071) {
  ulong popcnt(ulong x) {
    x = (x & 0x5555555555555555L) + (x>> 1 & 0x5555555555555555L);
    x = (x & 0x3333333333333333L) + (x>> 2 & 0x3333333333333333L);
    x = (x & 0x0f0f0f0f0f0f0f0fL) + (x>> 4 & 0x0f0f0f0f0f0f0f0fL);
    x = (x & 0x00ff00ff00ff00ffL) + (x>> 8 & 0x00ff00ff00ff00ffL);
    x = (x & 0x0000ffff0000ffffL) + (x>>16 & 0x0000ffff0000ffffL);
    x = (x & 0x00000000ffffffffL) + (x>>32 & 0x00000000ffffffffL);
    return x;
  }
}


Measured memory_bytes: 25060