Consolidated Warehouse Stock Ledger

Two warehouses each keep a stock ledger: a list of entries (sku, count) giving the number of units on hand for a SKU code. Within a single ledger every SKU code is distinct and the entries are already listed in strictly increasing order of SKU code.

You must produce one consolidated ledger covering both warehouses: for a SKU that appears in only one of the two ledgers, its count in the consolidated ledger is exactly that count; for a SKU that appears in both ledgers, its count in the consolidated ledger is the sum of the two counts. The consolidated ledger must list every distinct SKU exactly once, sorted in strictly increasing order of SKU code.

Input format

The first line contains an integer n, the number of entries in the first warehouse's ledger. Each of the next n lines contains two integers sku and count for that ledger, given in strictly increasing order of sku. The next line contains an integer m, the number of entries in the second warehouse's ledger, followed by m lines of sku and count in the same format, also strictly increasing by sku.

Output format

Print an integer k, the number of distinct SKUs in the consolidated ledger, on its own line. Then print k lines, each containing a SKU code and its consolidated count, sorted in strictly increasing order of SKU code.

Constraints

• 1 <= n, m <= 1000
• 1 <= sku <= 1000000
• 0 <= count <= 1000
• Within each ledger, all sku values are distinct and strictly increasing as listed in the input.

3
10 5
20 3
50 7
3
10 2
30 4
50 1

4
10 7
20 3
30 4
50 8

2
5 9
8 2
3
3 6
8 5
12 1

4
3 6
5 9
8 7
12 1