Weightlifter

Time limit1sMemory limit1024 MB

Summary

Sum the evening-minus-morning body mass increases on training days to get the total muscle gain.

Level: Easy2 of 10
Topics: Implementation, Array
Solved: No attempts yet

Problem

A weightlifter is preparing for a competition and wants to analyze the muscle mass he has gained. He reviews his training records for the last $n$ days. For each day, his body mass in the morning $x_i$ and in the evening $y_i$ are known. It is also known on which days he trained.

On training days, an increase in body mass, if it happened, counts as a gain in muscle mass. If his body mass decreased or he did not train, the muscle gain for that day is $0$ .

Help the weightlifter find his total gain in muscle mass.

Input

The first line contains $n$ , the number of days to analyze ( $1 \le n \le 1000$ ).

The second line contains $n$ integers. The $i$ -th integer is $1$ if there was training on day $i$ , and $0$ if there was no training on day $i$ .

The next $n$ lines contain the body mass measurements. Each line has two integers $x_i$ and $y_i$ , the body mass in grams ( $30\,000 \le x_i, y_i \le 200\,000$ ).

Output

Print one integer, the total gain in muscle mass.

Examples1

Example 1

Input

5
0 1 0 1 0
80000 81000
80500 81500
81500 81000
80500 80000
80000 81800

Expected output