Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                if dists[ny][nx] <= dists[y][x] + 2: break # gori~~
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                if dists[ny][nx] <= dists[y][x] + 4: break # gori~~
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                if dists[ny][nx] <= dists[y][x] + 10: break # gori~~
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

from collections import deque
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')
dists = [[INF]*W for _ in range(H)]
dists[r1][c1] = 0
q = deque([(r1,c1)])
while q:
    y,x = q.popleft()
    if y==r2 and x==c2:
        print(dists[y][x])
        exit()
    for dx,dy in dxy:
        for i in range(1,K+1):
            nx,ny = x+dx*i,y+dy*i
            if not 0 <= nx < W: break
            if not 0 <= ny < H: break
            if C[ny][nx] == '@': break
            if dists[ny][nx] <= dists[y][x] + 1: continue
            dists[ny][nx] = dists[y][x] + 1
            q.append((ny,nx))
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

import heapq
from collections import deque
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')

dists = [[INF]*W for _ in range(H)]
dists[r1][c1] = 0
q = deque([(r1,c1)])
while q:
    y,x = q.popleft()
    for dx,dy in dxy:
        nx,ny = x+dx,y+dy
        if not 0 <= nx < W: continue
        if not 0 <= ny < H: continue
        if C[ny][nx] == '@': continue
        if dists[ny][nx] <= dists[y][x] + 1: continue
        dists[ny][nx] = dists[y][x] + 1
        q.append((ny,nx))

costs = [INF] * (H*W*4)
costs[(r1*W+c1)*4] = 0
hq = [(r1*W+c1)*4]
heapq.heapify(hq)
while hq:
    v = heapq.heappop(hq)
    cp,d = divmod(v,4)
    cy,x = divmod(cp,W)
    c,y = divmod(cy,H)
    if y==r2 and x==c2:
        print(0--c//K)
        exit()
    for di,(dx,dy) in enumerate(dxy):
        nx,ny = x+dx,y+dy
        if not 0 <= nx < W: continue
        if not 0 <= ny < H: continue
        if dists[ny][nx] >= dists[y][x] + 20: continue
        if C[ny][nx] == '@': continue
        if di != d:
            nc = c + (K-c)%K
            if costs[(y*W+x)*4+di] <= nc: continue
            costs[(y*W+x)*4+di] = nc
            heapq.heappush(hq, ((nc*H+y)*W+x)*4+di)
        else:
            if costs[(ny*W+nx)*4+di] <= c+1: continue
            heapq.heappush(hq, (((c+1)*H+ny)*W+nx)*4+di)
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

import heapq
from collections import deque
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')

dists = [[INF]*W for _ in range(H)]
dists[r1][c1] = 0
q = deque([(r1,c1)])
while q:
    y,x = q.popleft()
    for dx,dy in dxy:
        nx,ny = x+dx,y+dy
        if not 0 <= nx < W: continue
        if not 0 <= ny < H: continue
        if C[ny][nx] == '@': continue
        if dists[ny][nx] <= dists[y][x] + 1: continue
        dists[ny][nx] = dists[y][x] + 1
        q.append((ny,nx))

costs = [INF] * (H*W*4)
costs[(r1*W+c1)*4] = 0
hq = [(r1*W+c1)*4]
heapq.heapify(hq)
while hq:
    v = heapq.heappop(hq)
    cp,d = divmod(v,4)
    cy,x = divmod(cp,W)
    c,y = divmod(cy,H)
    if y==r2 and x==c2:
        print(0--c//K)
        exit()
    for di,(dx,dy) in enumerate(dxy):
        nx,ny = x+dx,y+dy
        if not 0 <= nx < W: continue
        if not 0 <= ny < H: continue
        if dists[ny][nx] >= dists[y][x] + 100: continue
        if C[ny][nx] == '@': continue
        if di != d:
            nc = c + (K-c)%K
            if costs[(y*W+x)*4+di] <= nc: continue
            costs[(y*W+x)*4+di] = nc
            heapq.heappush(hq, ((nc*H+y)*W+x)*4+di)
        else:
            if costs[(ny*W+nx)*4+di] <= c+1: continue
            heapq.heappush(hq, (((c+1)*H+ny)*W+nx)*4+di)
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

import heapq
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')

dists = [INF] * (H*W*4)
dists[(r1*W+c1)*4] = 0
hq = [(r1*W+c1)*4]
heapq.heapify(hq)
while hq:
    v = heapq.heappop(hq)
    cp,d = divmod(v,4)
    cy,x = divmod(cp,W)
    c,y = divmod(cy,H)
    if y==r2 and x==c2:
        print(0--c//K)
        exit()
    for di,(dx,dy) in enumerate(dxy):
        nx,ny = x+dx,y+dy
        if not 0 <= nx < W: continue
        if not 0 <= ny < H: continue
        if C[ny][nx] == '@': continue
        if di != d:
            nc = c + (K-c)%K
            if dists[(y*W+x)*4+di] <= nc: continue
            dists[(y*W+x)*4+di] = nc
            heapq.heappush(hq, ((nc*H+y)*W+x)*4+di)
        else:
            if dists[(ny*W+nx)*4+di] <= c+1: continue
            heapq.heappush(hq, (((c+1)*H+ny)*W+nx)*4+di)
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

import heapq
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')

dists = [INF] * (H*W*4)
dists[(r1*W+c1)*4] = 0
hq = [(r1*W+c1)*4]
heapq.heapify(hq)
while hq:
    v = heapq.heappop(hq)
    cp,d = divmod(v,4)
    cy,x = divmod(cp,W)
    c,y = divmod(cy,H)
    if y==r2 and x==c2:
        print(0--c//K)
        exit()
    for di,(dx,dy) in enumerate(dxy):
        nx,ny = x+dx,y+dy
        if not 0 <= nx < W: continue
        if not 0 <= ny < H: continue
        if C[ny][nx] == '@': continue
        if di != d:
            nc = c + (K-c)%K
            if dists[(y*W+x)*4+di] <= nc: continue
            dists[(y*W+x)*4+di] = nc
            heapq.heappush(hq, ((nc*H+y)*W+x)*4+di)
        else:
            if dists[(ny*W+nx)*4+di] <= c+1: continue
            heapq.heappush(hq, (((c+1)*H+ny)*W+nx)*4+di)
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

import heapq
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')

dists = [[[INF]*4 for _ in range(W)] for _ in range(H)]
dists[r1][c1][0] = 0
hq = [(r1*W+c1)*4]
heapq.heapify(hq)
while hq:
    v = heapq.heappop(hq)
    cp,d = divmod(v,4)
    cy,x = divmod(cp,W)
    c,y = divmod(cy,H)
    if y==r2 and x==c2:
        print(0--c//K)
        exit()
    for di,(dx,dy) in enumerate(dxy):
        nx,ny = x+dx,y+dy
        if not 0 <= nx < W: continue
        if not 0 <= ny < H: continue
        if C[ny][nx] == '@': continue
        if di != d:
            nc = c + (K-c)%K
            if dists[y][x][di] <= nc: continue
            dists[y][x][di] = nc
            heapq.heappush(hq, ((nc*H+y)*W+x)*4+di)
        else:
            if dists[ny][nx][di] <= c+1: continue
            heapq.heappush(hq, (((c+1)*H+ny)*W+nx)*4+di)
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

import heapq
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')

dists = [[[INF]*4 for _ in range(W)] for _ in range(H)]
dists[r1][c1][0] = 0
hq = [(0,(r1*W+c1)*4)]
heapq.heapify(hq)
while hq:
    c,v = heapq.heappop(hq)
    p,d = divmod(v,4)
    y,x = divmod(p,W)
    if y==r2 and x==c2:
        print(0--c//K)
        exit()
    for di,(dx,dy) in enumerate(dxy):
        nx,ny = x+dx,y+dy
        if not 0 <= nx < W: continue
        if not 0 <= ny < H: continue
        if C[ny][nx] == '@': continue
        if di != d:
            nc = c + (K-c)%K
            if dists[y][x][di] <= nc: continue
            dists[y][x][di] = nc
            heapq.heappush(hq, (nc,p*4+di))
        else:
            if dists[ny][nx][di] <= c+1: continue
            heapq.heappush(hq, (c+1,(ny*W+nx)*4+di))
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

import heapq
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')

dists = [[[INF]*4 for _ in range(W)] for _ in range(H)]
dists[r1][c1][0] = 0
hq = [(0,(r1*W+c1)*4)]
heapq.heapify(hq)
while hq:
    c,v = heapq.heappop(hq)
    p,d = divmod(v,4)
    y,x = divmod(p,W)
    if y==r2 and x==c2:
        print(0--c//K)
        exit()
    for di,(dx,dy) in enumerate(dxy):
        if di != d:
            nc = c + (K-c)%K
            if dists[y][x][di] <= nc: continue
            dists[y][x][di] = nc
            heapq.heappush(hq, (nc,p*4+di))
        else:
            nx,ny = x+dx,y+dy
            if not 0 <= nx < W: continue
            if not 0 <= ny < H: continue
            if C[ny][nx] == '@': continue
            if dists[ny][nx][di] <= c+1: continue
            heapq.heappush(hq, (c+1,(ny*W+nx)*4+di))
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()

Buggy python submission (verdict: Time Limit Exceeded):
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

import heapq
dxy = [(0,1),(1,0),(0,-1),(-1,0)]
INF = float('inf')

dists = [[[INF]*4 for _ in range(W)] for _ in range(H)]
dists[r1][c1][0] = 0
hq = [(0,(r1*W+c1)*4)]
heapq.heapify(hq)
while hq:
    c,v = heapq.heappop(hq)
    p,d = divmod(v,4)
    y,x = divmod(p,W)
    if y==r2 and x==c2:
        print(0--c//K)
        exit()
    for di,(dx,dy) in enumerate(dxy):
        if di != d:
            nc = c + (K-c)%K
            if dists[y][x][di] <= nc: continue
            dists[y][x][di] = nc
            heapq.heappush(hq, (nc,p*4+di))
        else:
            nx,ny = x+dx,y+dy
            if not 0 <= nx < W: continue
            if not 0 <= ny < H: continue
            if C[ny][nx] == '@': continue
            if dists[ny][nx][di] <= c+1: continue
            heapq.heappush(hq, (c+1,(ny*W+nx)*4+di))
print(-1)

Fixed submission:
import sys
input = sys.stdin.readline
H,W,K = map(int,input().split())
r1,c1,r2,c2 = map(lambda x:int(x)-1,input().split())
C = [input() for i in range(H)]

def solve():
    from collections import deque
    dxy = [(0,1),(1,0),(0,-1),(-1,0)]
    INF = float('inf')
    dists = [[INF]*W for _ in range(H)]
    dists[r1][c1] = 0
    q = deque([(r1,c1)])
    while q:
        y,x = q.popleft()
        if y==r2 and x==c2:
            print(dists[y][x])
            exit()
        for dx,dy in dxy:
            for i in range(1,K+1):
                nx,ny = x+dx*i,y+dy*i
                if not 0 <= nx < W: break
                if not 0 <= ny < H: break
                if C[ny][nx] == '@': break
                if dists[ny][nx] <= dists[y][x]: break
                if dists[ny][nx] <= dists[y][x] + 1: continue
                dists[ny][nx] = dists[y][x] + 1
                q.append((ny,nx))
    print(-1)
solve()