Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N) + na + [default] * (self.N-n)
            for i in range(self.N-1,0,-1):
                self.A[i] = func(self.A[i*2], self.A[i*2+1])
        else:
            self.A = [default] * (self.N*2)
        self.F = func

    def find(self, i):
        return self.A[i + self.N]

    def update(self, i, x):
        i += self.N
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2], self.A[i*2+1])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        A = self.A
        l = a + self.N
        r = b + self.N
        res = self.D
        while l < r:
            if l % 2 == 1:
                res = self.merge(res, A[l])
                l += 1
            if r % 2 == 1:
                r -= 1
                res = self.merge(res, A[r])
            l >>= 1
            r >>= 1

        return res

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti))
        if ui - ti > 1:
            nl.append((ti+1, ui))
        if ui < r-1:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())





Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N) + na + [default] * (self.N-n)
            for i in range(self.N-1,0,-1):
                self.A[i] = func(self.A[i*2], self.A[i*2+1])
        else:
            self.A = [default] * (self.N*2)
        self.F = func

    def find(self, i):
        return self.A[i + self.N]

    def update(self, i, x):
        i += self.N
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2], self.A[i*2+1])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        A = self.A
        l = a + self.N
        r = b + self.N
        res = self.D
        while l < r:
            if l % 2 == 1:
                res = self.merge(res, A[l])
                l += 1
            if r % 2 == 1:
                r -= 1
                res = self.merge(res, A[r])
            l >>= 1
            r >>= 1

        return res

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti))
        if ui - ti > 1:
            nl.append((ti+1, ui))
        if ui < r-1:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N-1) + na + [default] * (self.N-n)
            for i in range(self.N-2,-1,-1):
                self.A[i] = func(self.A[i*2+1], self.A[i*2+2])
        else:
            self.A = [default] * (self.N*2-1)
        self.F = func

    def find(self, i):
        return self.A[i + self.N - 1]

    def update(self, i, x):
        i += self.N - 1
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2+1], self.A[i*2+2])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        b += 1
        def _query(k,l,r):
            if r <= a or b <= l:
                return self.D
            if a <= l and r <= b:
                return self.A[k]
            m = (l+r)//2
            vl = _query(k*2+1,l,m)
            vr = _query(k*2+2,m,r)
            return self.merge(vl,vr)
        return _query(0,0,self.N)

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti-1))
        if ui - ti > 1:
            nl.append((ti+1, ui-1))
        if ui < r:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n-1))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())





Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N) + na + [default] * (self.N-n)
            for i in range(self.N-1,0,-1):
                self.A[i] = func(self.A[i*2], self.A[i*2+1])
        else:
            self.A = [default] * (self.N*2)
        self.F = func

    def find(self, i):
        return self.A[i + self.N]

    def update(self, i, x):
        i += self.N
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2], self.A[i*2+1])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        A = self.A
        l = a + self.N
        r = b + self.N
        res = self.D
        while l < r:
            if l % 2 == 1:
                res = self.merge(res, A[l])
                l += 1
            if r % 2 == 1:
                r -= 1
                res = self.merge(res, A[r])
            l >>= 1
            r >>= 1

        return res

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti))
        if ui - ti > 1:
            nl.append((ti+1, ui))
        if ui < r-1:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = math.ceil(math.log2(n))
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N-1) + na + [default] * (self.N-n)
            for i in range(self.N-2,-1,-1):
                self.A[i] = func(self.A[i*2+1], self.A[i*2+2])
        else:
            self.A = [default] * (self.N*2-1)
        self.F = func

    def find(self, i):
        return self.A[i + self.N - 1]

    def update(self, i, x):
        i += self.N - 1
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2+1], self.A[i*2+2])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        b += 1
        def _query(k,l,r):
            if r <= a or b <= l:
                return self.D
            if a <= l and r <= b:
                return self.A[k]
            m = (l+r)//2
            vl = _query(k*2+1,l,m)
            vr = _query(k*2+2,m,r)
            return self.merge(vl,vr)
        return _query(0,0,self.N)

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti-1))
        if ui - ti > 1:
            nl.append((ti+1, ui-1))
        if ui < r:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n-1))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())





Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N) + na + [default] * (self.N-n)
            for i in range(self.N-1,0,-1):
                self.A[i] = func(self.A[i*2], self.A[i*2+1])
        else:
            self.A = [default] * (self.N*2)
        self.F = func

    def find(self, i):
        return self.A[i + self.N]

    def update(self, i, x):
        i += self.N
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2], self.A[i*2+1])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        A = self.A
        l = a + self.N
        r = b + self.N
        res = self.D
        while l < r:
            if l % 2 == 1:
                res = self.merge(res, A[l])
                l += 1
            if r % 2 == 1:
                r -= 1
                res = self.merge(res, A[r])
            l >>= 1
            r >>= 1

        return res

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti))
        if ui - ti > 1:
            nl.append((ti+1, ui))
        if ui < r-1:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())

Buggy python submission (verdict: Runtime Error):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = math.ceil(math.log2(n))
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N-1) + na + [default] * (self.N-n)
            for i in range(self.N-2,-1,-1):
                self.A[i] = func(self.A[i*2+1], self.A[i*2+2])
        else:
            self.A = [default] * (self.N*2-1)
        self.F = func

    def find(self, i):
        return self.A[i + self.N - 1]

    def update(self, i, x):
        i += self.N - 1
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2+1], self.A[i*2+2])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        b += 1
        def _query(k,l,r):
            if r <= a or b <= l:
                return self.D
            if a <= l and r <= b:
                return self.A[k]
            m = (l+r)//2
            vl = _query(k*2+1,l,m)
            vr = _query(k*2+2,m,r)
            return self.merge(vl,vr)
        return _query(0,0,self.N)

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti-1))
        if ui - ti > 1:
            nl.append((ti+1, ui-1))
        if ui < r:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n-1))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())





Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N) + na + [default] * (self.N-n)
            for i in range(self.N-1,0,-1):
                self.A[i] = func(self.A[i*2], self.A[i*2+1])
        else:
            self.A = [default] * (self.N*2)
        self.F = func

    def find(self, i):
        return self.A[i + self.N]

    def update(self, i, x):
        i += self.N
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2], self.A[i*2+1])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        A = self.A
        l = a + self.N
        r = b + self.N
        res = self.D
        while l < r:
            if l % 2 == 1:
                res = self.merge(res, A[l])
                l += 1
            if r % 2 == 1:
                r -= 1
                res = self.merge(res, A[r])
            l >>= 1
            r >>= 1

        return res

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti))
        if ui - ti > 1:
            nl.append((ti+1, ui))
        if ui < r-1:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9 + 7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, n, default, func):
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        self.A = [default] * (self.N*2-1)
        self.F = func

    def find(self, i):
        return self.A[i + self.N - 1]

    def update(self, i, x):
        i += self.N - 1
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2+1], self.A[i*2+2])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        b += 1
        def _query(k,l,r):
            if r <= a or b <= l:
                return self.D
            if a <= l and r <= b:
                return self.A[k]
            m = (l+r)//2
            vl = _query(k*2+1,l,m)
            vr = _query(k*2+2,m,r)
            return self.merge(vl,vr)
        return _query(0,0,self.N)

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg(n,inf,sf)
    s2 = Seg(n,inf,sf)
    d = {}

    for i in range(n):
        if i % 2 == 0:
            s1.update(i, a[i])
        else:
            s2.update(i, a[i])
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti-1))
        if ui - ti > 1:
            nl.append((ti+1, ui-1))
        if ui < r:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n-1))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N) + na + [default] * (self.N-n)
            for i in range(self.N-1,0,-1):
                self.A[i] = func(self.A[i*2], self.A[i*2+1])
        else:
            self.A = [default] * (self.N*2)
        self.F = func

    def find(self, i):
        return self.A[i + self.N]

    def update(self, i, x):
        i += self.N
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2], self.A[i*2+1])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        A = self.A
        l = a + self.N
        r = b + self.N
        res = self.D
        while l < r:
            if l % 2 == 1:
                res = self.merge(res, A[l])
                l += 1
            if r % 2 == 1:
                r -= 1
                res = self.merge(res, A[r])
            l >>= 1
            r >>= 1

        return res

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti))
        if ui - ti > 1:
            nl.append((ti+1, ui))
        if ui < r-1:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9 + 7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, n, default, func):
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        self.A = [default] * (self.N*2-1)
        self.F = func

    def find(self, i):
        return self.A[i + self.N - 1]

    def update(self, i, x):
        i += self.N - 1
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2+1], self.A[i*2+2])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        b += 1
        def _query(k,l,r):
            if r <= a or b <= l:
                return self.D
            if a <= l and r <= b:
                return self.A[k]
            m = (l+r)//2
            vl = _query(k*2+1,l,m)
            vr = _query(k*2+2,m,r)
            return self.merge(vl,vr)
        return _query(0,0,self.N)

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg(n,(inf,-1),sf)
    s2 = Seg(n,(inf,-1),sf)

    for i in range(n):
        if i % 2 == 0:
            s1.update(i, (a[i], i))
        else:
            s2.update(i, (a[i], i))

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            u = s2.query(t[1]+1,r)
        else:
            t = s2.query(l,r)
            u = s1.query(t[1]+1,r)
        nl = []
        if l < t[1]:
            nl.append((l, t[1]-1))
        if u[1] - t[1] > 1:
            nl.append((t[1]+1, u[1]-1))
        if u[1] < r:
            nl.append((u[1]+1, r))
        return ((t[0],u[0]), nl)

    q = []
    heapq.heappush(q, f(0,n-1))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N) + na + [default] * (self.N-n)
            for i in range(self.N-1,0,-1):
                self.A[i] = func(self.A[i*2], self.A[i*2+1])
        else:
            self.A = [default] * (self.N*2)
        self.F = func

    def find(self, i):
        return self.A[i + self.N]

    def update(self, i, x):
        i += self.N
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2], self.A[i*2+1])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        A = self.A
        l = a + self.N
        r = b + self.N
        res = self.D
        while l < r:
            if l % 2 == 1:
                res = self.merge(res, A[l])
                l += 1
            if r % 2 == 1:
                r -= 1
                res = self.merge(res, A[r])
            l >>= 1
            r >>= 1

        return res

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti))
        if ui - ti > 1:
            nl.append((ti+1, ui))
        if ui < r-1:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9 + 7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, n, default, func):
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        self.A = [default] * (self.N*2-1)
        self.F = func

    def find(self, i):
        return self.A[i + self.N - 1]

    def update(self, i, x):
        i += self.N - 1
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2+1], self.A[i*2+2])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        b += 1
        def _query(k,l,r):
            if r <= a or b <= l:
                return self.D
            if a <= l and r <= b:
                return self.A[k]
            m = (l+r)//2
            vl = _query(k*2+1,l,m)
            vr = _query(k*2+2,m,r)
            return self.merge(vl,vr)
        return _query(0,0,self.N)

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg(n,(inf,-1),sf)
    s2 = Seg(n,(inf,-1),sf)

    for i in range(n):
        if i % 2 == 0:
            s1.update(i, (a[i], i))
        else:
            s2.update(i, (a[i], i))

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            u = s2.query(t[1]+1,r)
        else:
            t = s2.query(l,r)
            u = s1.query(t[1]+1,r)
        nl = []
        if l < t[1]:
            nl.append((l, t[1]-1))
        if u[1] - t[1] > 1:
            nl.append((t[1]+1, u[1]-1))
        if u[1] < r:
            nl.append((u[1]+1, l))
        return ((t[0],u[0]), nl)

    q = []
    heapq.heappush(q, f(0,n-1))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
gosa = 1.0 / 10**10
mod = 10**9+7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class Seg():
    def __init__(self, na, default, func):
        if isinstance(na, list):
            n = len(na)
        else:
            n = na
        i = 1
        while 2**i <= n:
            i += 1
        self.D = default
        self.H = i
        self.N = 2**i
        if isinstance(na, list):
            self.A = [default] * (self.N) + na + [default] * (self.N-n)
            for i in range(self.N-1,0,-1):
                self.A[i] = func(self.A[i*2], self.A[i*2+1])
        else:
            self.A = [default] * (self.N*2)
        self.F = func

    def find(self, i):
        return self.A[i + self.N]

    def update(self, i, x):
        i += self.N
        self.A[i] = x
        while i > 0:
            i = (i-1) // 2
            self.A[i] = self.merge(self.A[i*2], self.A[i*2+1])

    def merge(self, a, b):
        return self.F(a, b)

    def total(self):
        return self.A[0]

    def query(self, a, b):
        A = self.A
        l = a + self.N
        r = b + self.N
        res = self.D
        while l < r:
            if l % 2 == 1:
                res = self.merge(res, A[l])
                l += 1
            if r % 2 == 1:
                r -= 1
                res = self.merge(res, A[r])
            l >>= 1
            r >>= 1

        return res

def main():
    n = I()
    a = LI()

    def sf(a,b):
        if a < b:
            return a
        return b

    s1 = Seg([c if i%2==0 else inf for c,i in zip(a,range(n))],inf,sf)
    s2 = Seg([c if i%2==1 else inf for c,i in zip(a,range(n))],inf,sf)
    d = {}

    for i in range(n):
        d[a[i]] = i

    def f(l,r):
        if l % 2 == 0:
            t = s1.query(l,r)
            ti = d[t]
            u = s2.query(ti+1,r)
        else:
            t = s2.query(l,r)
            ti = d[t]
            u = s1.query(ti+1,r)
        ui = d[u]
        nl = []
        if l < ti:
            nl.append((l, ti))
        if ui - ti > 1:
            nl.append((ti+1, ui))
        if ui < r-1:
            nl.append((ui+1, r))
        return ((t,u), nl)

    q = []
    heapq.heappush(q, f(0,n))
    r = []
    while q:
        t,nl = heapq.heappop(q)
        r.append(t[0])
        r.append(t[1])
        for t,u in nl:
            heapq.heappush(q, f(t,u))

    return ' '.join(map(str,r))

print(main())