Little Susie loves strings. Today she calculates distances between them. As Susie is a small girl after all, her strings contain only digits zero and one. She uses the definition of Hamming distance:

We will define the distance between two strings *s* and *t* of the same length consisting of digits zero and one as the number of positions *i*, such that *s*<sub class="lower-index">*i*</sub> isn't equal to *t*<sub class="lower-index">*i*</sub>. 

As besides everything else Susie loves symmetry, she wants to find for two strings *s* and *t* of length *n* such string *p* of length *n*, that the distance from *p* to *s* was equal to the distance from *p* to *t*.

It's time for Susie to go to bed, help her find such string *p* or state that it is impossible.
The first line contains string *s* of length *n*. 

The second line contains string *t* of length *n*.

The length of string *n* is within range from 1 to 10<sup class="upper-index">5</sup>. It is guaranteed that both strings contain only digits zero and one.
n = int(input())
tree = [] # empty list
for i in range(n):
    tree.append(list(map(int,input().split())))
s = 2
t = sorted(tree,reverse = True)
t = sorted(tree) # arrange in ascending order

for j in range(1,-1):
    a,b = tree[i]
    if x - tree[i-1][0] > b:
        s += 1
    elif tree[i-1][0] -x >b:
        s += 1
        tree[i][0] += b
print(s if n>1 else 1)