def ii():return int(input())
def iim():return map(int,input().split())
def iil():return list(map(int,input().split()))
from collections import deque


def bfs(xg,yg):
    queue = deque([(xs,ys,0)])
    while queue:
        x,y,dep = queue.popleft()
        l = []
        f1 = True
        f2 = True
        f3 = True
        f4 = True
        for i in range(1,k+1):
            if f1:
                if cord[y][x+i] == '.':
                    l.append((x+i,y))
                elif cord[y][x+i] == '@' or cord[y][x+i] != dep+1:
                    f1 = False
            if f2:
                if cord[y][x-i] == '.':
                    l.append((x-i,y))
                elif cord[y][x-i] == '@' or cord[y][x+i] != dep+1:
                    f2 = False
            if f3:
                if cord[y+i][x] == '.':
                    l.append((x,y+i))
                elif cord[y+i][x] == '@' or cord[y][x+i] != dep+1:
                    f3 = False
            if f4:
                if cord[y-i][x] == '.':
                    l.append((x,y-i))
                elif cord[y-i][x] == '@' or cord[y][x+i] != dep+1:
                    f4 = False
            if not (f1 or f2 or f3 or f4):
                break
        for nx, ny in l:
            if cord[ny][nx] == '.':
                cord[ny][nx] = dep+1
                if (nx,ny) == (xg,yg):
                    return dep+1
                else:
                    queue.append((nx,ny,dep+1))
    return -1

h,w,k = iim()
ys,xs,yg,xg = iim()

cord = [['@']*(w+2)]
for i in range(h):
    cord.append(['@']+list(input())+['@'])
cord.append(['@']*(w+2))
cord[ys][xs] = '#'
#for i in cord:
#    print(*i)
print(bfs(xg,yg))


### FIXED CODE ###

def ii():return int(input())
def iim():return map(int,input().split())
def iil():return list(map(int,input().split()))
from collections import deque


def bfs(xg,yg):
    queue = deque([(xs,ys,0)])
    while queue:
        x,y,dep = queue.popleft()
        l = []
        f1 = True
        f2 = True
        f3 = True
        f4 = True
        for i in range(1,k+1):
            if f1:
                if cord[y][x+i] == '.':
                    l.append((x+i,y))
                elif cord[y][x+i] == '@' or cord[y][x+i] != dep+1:
                    f1 = False
            if f2:
                if cord[y][x-i] == '.':
                    l.append((x-i,y))
                elif cord[y][x-i] == '@' or cord[y][x-i] != dep+1:
                    f2 = False
            if f3:
                if cord[y+i][x] == '.':
                    l.append((x,y+i))
                elif cord[y+i][x] == '@' or cord[y+i][x] != dep+1:
                    f3 = False
            if f4:
                if cord[y-i][x] == '.':
                    l.append((x,y-i))
                elif cord[y-i][x] == '@' or cord[y-i][x] != dep+1:
                    f4 = False
            if not (f1 or f2 or f3 or f4):
                break
        for nx, ny in l:
            if cord[ny][nx] == '.':
                cord[ny][nx] = dep+1
                if (nx,ny) == (xg,yg):
                    return dep+1
                else:
                    queue.append((nx,ny,dep+1))
    return -1

h,w,k = iim()
ys,xs,yg,xg = iim()

cord = [['@']*(w+2)]
for i in range(h):
    cord.append(['@']+list(input())+['@'])
cord.append(['@']*(w+2))
cord[ys][xs] = '#'
#for i in cord:
#    print(*i)
#print(len(cord),len(cord[0]))

print(bfs(xg,yg))