from random import shuffle,randint
import sys

def swap(a,i,e):
    tmp = a[i]
    a[i] = a[e]
    a[e] = tmp
    

def restore(a,m):
    for i in range(0,len(a)):
        a[i] += m

def findSmallestMissing(a):
    n = len(a)
    m = min(a)
    for i in range(0,n):
        a[i] = a[i] -m
    
    i = 0
    n = len(a)
    while (i < n):
        print('| ',i,'|',n,'|',a[0:i],'|', a[i:n],'|',a[n:len(a)], '||')
        if (a[i] == i): # a[i] already equals i, nothing more to do
            i=i+1
        else:
            if (a[i] < i):    # a[i] is strictly less than i
                              # This means a[i] is a repeated element and cannot be missing
                swap(a,i,n-1) # Place a[i] in the range of elements that cannot be the missing one
                n=n-1         # reduce n by 1
            else:
                e=a[i]        # Let us call e = a[i]
                if (e <  n):  
                    if (a[e] == e):  # if a[e] already has e in it, e cannot be missing
                        swap(a,i,n-1)  
                        n = n -1
                    else:            # otherwise, place a[e] = e and bring a[i] = a[e]
                        e = a[i]
                        swap(a,i,e)
                else:                # if e >= n
                    swap(a,i,n-1)    # then a[i] cannot be missing
                    n = n-1
    print('| ',i,'|',n,'|',a[0:i],'|',a[i:n],'|',a[n:len(a)], '')
    for i in range(0,n):
        if (a[i] != i):
            restore(a,m)
            print ( (i+m),' is missing')
            return (i+m)
    restore(a,m)
    print( (n+m), 'is missing')
    return (n+m)


# def test(n):
#     # Create an array of elements in the range 0, n
#     a=[]
#     for i in range(0,n):
#         a.append(i)
#     shuffle(a) # scramble
#     print(a)
#     # Now mess up 10 elements
#     r = randint(5,n-1)
#     m = n
#     for k in range(0,10):
#         j = randint(0,n-1)
#         if (a[j] >= r):
#             m = min(m,a[j])
#             print('Delete:',j,a[j])
#             a[j] = n + randint(2,n) # Just increase a[j]   
#     r = findSmallestMissing(a)
#     if (r == m):
#         return
#     else:
#         print('Failed: ')
#         print('\t a: ',a)
#         print('\t Smallest missing should be :',m,' your code says: ',r)
#         sys.exit(1)


# for i in range(0,50000):
#     test(100)


#findSmallestMissing([11,3,2,0,4,6,7,9,1,11,13,11])

findSmallestMissing([0,3,2,0,4,6,7,9,1,11,13,11])