Buggy python submission (verdict: Runtime Error):
def warshall_floid(d):
    for k in range(1,n+1):
        for i in range(1,n+1):
            for j in range(1,n+1):
                d[i][j] = min(d[i][j],d[i][k]+d[k][j])
    return d

n,m,l = map(int,input().split())
d = [10**13]*(n+1) for i in range(n+1)]
for i in range(m):
    a,b,c = map(int,input().split())
    d[a][b] = c
    d[b][a] = c
for i in range(1,n+1):
    d[i][i] = 0
d = warshall_floid(d)
for i in range(1,n+1):
    for j in range(1,n+1):
        if d[i][j] <= l:
            d[i][j] = 1
        else:
            d[i][j] = 10**13
d = warshall_floid(d)
q = int(input())
for i in range(q):
    s,t = map(int,input().split())
    if d[s][t] >= 10**13:
        print(-1)
    else:
        print(d[s][t]-1)


Fixed submission:
def warshall_floid(d):
    for k in range(1,n+1):
        for i in range(1,n+1):
            for j in range(1,n+1):
                d[i][j] = min(d[i][j],d[i][k]+d[k][j])
    return d

n,m,l = map(int,input().split())
d = [[10**13]*(n+1) for i in range(n+1)]
for i in range(m):
    a,b,c = map(int,input().split())
    d[a][b] = c
    d[b][a] = c
for i in range(1,n+1):
    d[i][i] = 0
d = warshall_floid(d)
for i in range(1,n+1):
    for j in range(1,n+1):
        if d[i][j] <= l:
            d[i][j] = 1
        else:
            d[i][j] = 10**13
d = warshall_floid(d)
q = int(input())
for i in range(q):
    s,t = map(int,input().split())
    if d[s][t] >= 10**13:
        print(-1)
    else:
        print(d[s][t]-1)

Buggy python submission (verdict: Runtime Error):
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

def warshall_floid(d):
    for k in range(1,n+1):
        for i in range(1,n+1):
            for j in range(1,n+1):
                d[i][j] = min(d[i][j],d[i][k]+d[k][j])
    return d
n,m,l = map(int,readline().split())
d = [[5*10**11]*(n+1) for i in range(n+1)]
for i in range(m):
    a,b,c = map(int,readline().split())
    d[a][b] = c
    d[b][a] = c
for i in range(1,n+1):
    d[i][i] = 0
d = warshall_floid(d)
for i in range(1,n+1):
    for j in range(1,n+1):
        if d[i][j] <= l:
            d[i][j] = 1
        else:
            d[i][j] = 5*10**11
d = warshall_floid(d)
q = int(input())
for i in range(q):
    s,t = map(int,readline().split())
    if d[s][t] >3*10**11:
        print(-1)
    else:
        print(d[s][t]-1)


Fixed submission:
def warshall_floid(d):
    for k in range(1,n+1):
        for i in range(1,n+1):
            for j in range(1,n+1):
                d[i][j] = min(d[i][j],d[i][k]+d[k][j])
    return d

n,m,l = map(int,input().split())
d = [[10**13]*(n+1) for i in range(n+1)]
for i in range(m):
    a,b,c = map(int,input().split())
    d[a][b] = c
    d[b][a] = c
for i in range(1,n+1):
    d[i][i] = 0
d = warshall_floid(d)
for i in range(1,n+1):
    for j in range(1,n+1):
        if d[i][j] <= l:
            d[i][j] = 1
        else:
            d[i][j] = 10**13
d = warshall_floid(d)
q = int(input())
for i in range(q):
    s,t = map(int,input().split())
    if d[s][t] >= 10**13:
        print(-1)
    else:
        print(d[s][t]-1)

Buggy python submission (verdict: Time Limit Exceeded):
def warshall_floid(d):
    for k in range(1,n+1):
        for i in range(1,n+1):
            for j in range(1,n+1):
                d[i][j] = min(d[i][j],d[i][k]+d[k][j])
    return d

n,m,l = map(int,input().split())
d = [[float('inf')]*(n+1) for i in range(n+1)]
for i in range(m):
    a,b,c = map(int,input().split())
    d[a][b] = c
    d[b][a] = c
for i in range(1,n+1):
    d[i][i] = 0
d = warshall_floid(d)
for i in range(1,n+1):
    for j in range(1,n+1):
        if d[i][j] <= l:
            d[i][j] = 1
        else:
            d[i][j] = float('inf')
d = warshall_floid(d)
q = int(input())
for i in range(q):
    s,t = map(int,input().split())
    if d[s][t] == float('inf'):
        print(-1)
    else:
        print(d[s][t]-1)


Fixed submission:
def warshall_floid(d):
    for k in range(1,n+1):
        for i in range(1,n+1):
            for j in range(1,n+1):
                d[i][j] = min(d[i][j],d[i][k]+d[k][j])
    return d

n,m,l = map(int,input().split())
d = [[10**13]*(n+1) for i in range(n+1)]
for i in range(m):
    a,b,c = map(int,input().split())
    d[a][b] = c
    d[b][a] = c
for i in range(1,n+1):
    d[i][i] = 0
d = warshall_floid(d)
for i in range(1,n+1):
    for j in range(1,n+1):
        if d[i][j] <= l:
            d[i][j] = 1
        else:
            d[i][j] = 10**13
d = warshall_floid(d)
q = int(input())
for i in range(q):
    s,t = map(int,input().split())
    if d[s][t] >= 10**13:
        print(-1)
    else:
        print(d[s][t]-1)