F = open( "27-51b.txt" ) 
  
 N = int(F.readline()) 
  
 sMin = 0 
 odd = 0 
 diff = [] 
 for i in range(N): 
   a, b = sorted( map(int, F.readline().split()) ) 
   odd += a % 2 
   if a % 2 != b % 2: 
     deltaEven = 1 if b % 2 == 0 else -1 
     diff.append( (abs(a-b), deltaEven, a, b) ) 
   sMin += a 
 F.close() 
  
 diff.sort() 
 even = N - odd 
  
 print( sMin, (even, odd) ) 
 #print( diff ) 
  
 if not(sMin % 2 != (odd > even)): 
   print( "Коррекция:" ) 
   while not(sMin % 2 != (odd > even)): 
     dS, deltaEven, a, b = diff.pop(0) 
     sMin += dS 
     odd -= deltaEven 
     even += deltaEven 
     print( sMin, (even, odd), b, '<-', a ) 
  
 print( "Ответ:", sMin ) 
  
 на следующее решение: 
 F = open( "27-51b.txt" ) 
  
 N = int(F.readline()) 
  
 sMin = 0 
 odd = 0 
 INF = 1e10 
 diff = [[INF, INF], [INF, INF]] 
 for i in range(N): 
   a, b = sorted( map(int, F.readline().split()) ) 
   odd += a % 2 
   if a % 2 != b % 2: 
     diff[b % 2].append( b-a ) 
   sMin += a 
 F.close() 
 print(diff) 
 even = N - odd 
 print( sMin, (even, odd) ) 
  
 diff[0] = sorted(diff[0])[:2] 
 diff[1] = sorted(diff[1])[:2] 
 print(diff) 
 delta0 = delta1 = 0 
 if sMin % 2 == (odd > even): 
   print( "Коррекция..." ) 
   print( diff[0] ) 
   print( diff[1] ) 
   if abs(even-odd) > 1: 
     delta0, delta1 = diff[0][0], diff[1][0] # добавить чётное или нечётное 
   elif even > odd: # even = odd + 1 
     delta0 = diff[0][0] # добавить чётное 
     delta1 = diff[1][0] + diff[1][1] # добавить два нечётных 
   else: # odd = even + 1 
     delta1 = diff[1][0] # добавить нечётное 
     delta0 = diff[0][0] + diff[0][1] # добавить два чётных 
   sMin += min(delta0, delta1) 
  
 print( "Ответ:", sMin )