Finding matching pairs

Time limit2sMemory limit512 MB

Summary

Given 2 to 10 integers and a target, print every position pair that sums to the target in lexicographic order, then the count.

Level: Easy3 of 10
Topics: Sorting, Brute force, Implementation
Solved: No attempts yet

Problem

The first line holds several integers and the second line holds one target value. Print every pair of numbers that sit at two different positions and sum to the target value, then print the number of such pairs on the last line.

Input

The first line has 2 to 10 integers separated by spaces. The second line has one integer, the target value. Every integer given is a natural number not greater than 100,000.

Output

Print one pair per line, then print the number of pairs on the last line.

Print a pair as $a$ and $b$ in that order on one line, with $a \le b$ . The pairs $(a, b)$ and $(b, a)$ have the same composition and count as one pair.

Pairs are counted by position. Print one line for each choice of two different positions $i < j$ that meets the condition, and count each choice separately even when an identical pair of values was already printed. For the input 1 1 2 with target value $3$ , print $(1, 2)$ on two lines and print the count $2$ .

When several pairs exist, print them in lexicographic order. $(a, b)$ comes before $(c, d)$ when $a < c$ , or when $a = c$ and $b < d$ .

When no pair meets the condition, print only the count $0$ .

Examples3

Example 1
Input
```
1 2
3
```
Expected output
```
1 2
1
```
Example 2
Input
```
1 2 3
100
```
Expected output
```
0
```
Example 3
Input
```
1 2 3 4 5
6
```
Expected output
```
1 5
2 4
2
```