# Original solution
N=int(eval(input()))
alist=list(map(int,input().split()))

def bs_left(mid,mp):
  sum2=abs(2*slist[mid]-slist[mp])
  if mid==0:
    sum1=sum2
  else:
    sum1=abs(2*slist[mid-1]-slist[mp])
  if mid==mp:
    sum3=sum2
  else:
    sum3=abs(2*slist[mid+1]-slist[mp])

  if sum2<=sum1 and sum2<=sum3:
    return 0
  elif sum1<sum2:
    return -1
  elif sum2>sum3:
    return 1    

def bs_right(mid,mp):
  sum2=abs(2*(slist[mid]-slist[mp])-(slist[-1]-slist[mp]))
  if mid==0:
    sum1=sum2
  else:
    sum1=abs(2*(slist[mid-1]-slist[mp])-(slist[-1]-slist[mp]))
  if mid==mp:
    sum3=sum2
  else:
    sum3=abs(2*(slist[mid+1]-slist[mp])-(slist[-1]-slist[mp]))

  if sum2<=sum1 and sum2<=sum3:
    return 0
  elif sum1<sum2:
    return -1
  elif sum2>sum3:
    return 1    
  
slist=[]
asum=0
for a in alist:
  asum+=a
  slist.append(asum)
#print(alist)
#print(slist)

dic_lp,dic_rp={},{}
for mp in range(1,N-2):  
  #lp
  l,r=0,mp-1
  while(l<=r):
    mid=(l+r)//2
    ret=bs_left(mid,mp)
    if ret==1:
      l=mid+1
    elif ret==-1:
      r=mid-1
    else:
      dic_lp[mp]=mid
      #print(mp,mid)
      break
  
  #rp
  l,r=mp+1,N-2
  while(l<=r):
    mid=(l+r)//2
    ret=bs_right(mid,mp)
    if ret==1:
      l=mid+1
    elif ret==-1:
      r=mid-1
    else:
      dic_rp[mp]=mid
      #print(mp,mid)
      break
    
min_diff=10**9
for mp in range(1,N-2):
  lp=dic_lp[mp]
  rp=dic_rp[mp]
  
  sum1=slist[lp]
  sum2=slist[mp]-slist[lp]
  sum3=slist[rp]-slist[mp]
  sum4=slist[-1]-slist[rp]
  #print(sum1,sum2,sum3,sum4)
  
  sum_list=[sum1,sum2,sum3,sum4]
  sum_list.sort()
  diff=sum_list[-1]-sum_list[0]
  #print(lp,mp,rp,diff)
  if diff<min_diff:
    min_diff=diff    
  
print(min_diff)


# Optimized solution
N=int(eval(input()))
alist=list(map(int,input().split()))

def bs_left(mid,mp):
  sum1=sum2=abs(2*slist[mid]-slist[mp])
  sum3=abs(2*slist[mid+1]-slist[mp])
  if mid>0:
    sum1=abs(2*slist[mid-1]-slist[mp])

  if sum2<=sum1 and sum2<=sum3:
    return 0
  elif sum1<sum2:
    return -1
  elif sum2>sum3:
    return 1    

def bs_right(mid,mp):
  sum1=abs(2*(slist[mid-1]-slist[mp])-(slist[-1]-slist[mp]))
  sum2=abs(2*(slist[mid]-slist[mp])-(slist[-1]-slist[mp]))
  sum3=abs(2*(slist[mid+1]-slist[mp])-(slist[-1]-slist[mp]))

  if sum2<=sum1 and sum2<=sum3:
    return 0
  elif sum1<sum2:
    return -1
  elif sum2>sum3:
    return 1    
  
slist=[]
asum=0
for a in alist:
  asum+=a
  slist.append(asum)
#print(alist)
#print(slist)

dic_lp,dic_rp={},{}
for mp in range(1,N-2):  
  #lp
  l,r=0,mp-1
  while(l<=r):
    mid=(l+r)//2
    ret=bs_left(mid,mp)
    if ret==1:
      l=mid+1
    elif ret==-1:
      r=mid-1
    else:
      dic_lp[mp]=mid
      #print(mp,mid)
      break
  
  #rp
  l,r=mp+1,N-2
  while(l<=r):
    mid=(l+r)//2
    ret=bs_right(mid,mp)
    if ret==1:
      l=mid+1
    elif ret==-1:
      r=mid-1
    else:
      dic_rp[mp]=mid
      #print(mp,mid)
      break
    
min_diff=10**9
for mp in range(1,N-2):
  lp=dic_lp[mp]
  rp=dic_rp[mp]
  
  sum1=slist[lp]
  sum2=slist[mp]-slist[lp]
  sum3=slist[rp]-slist[mp]
  sum4=slist[-1]-slist[rp]
  #print(sum1,sum2,sum3,sum4)
  
  sum_list=[sum1,sum2,sum3,sum4]
  sum_list.sort()
  diff=sum_list[-1]-sum_list[0]
  #print(lp,mp,rp,diff)
  if diff<min_diff:
    min_diff=diff    
  
print(min_diff)