import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        int lineNum;
        Scanner scanner = new Scanner(System.in);
        lineNum = Integer.parseInt(scanner.nextLine());
        String[] lines = new String[lineNum];
        for (int count = 0; count < lineNum; count++)
            lines[count] = scanner.nextLine();
        Days days = new Days(lines);
        //我以为是这个意思：记录每天超过8的部分。敲代码好慢
        int count = 0;
        for (int day = 0; day < days.num; day++) {
            int sum = days.get(day).sum;
            if (sum > 8)
                count += sum - 8;
        }
        System.out.println("-" + count);
    }
}

class Days {
    int[] sum, school, interest;
    int num/*天数用这个可以吧*/;

    Days(String[] lines) {
        num = lines.length;//只是太长了
        sum = new int[num];
        school = new int[num];
        interest = new int[num];//这样还是麻烦了
        for (int count = 0; count < num; count++) {
            String[] two = lines[count].split(" ");
            school[count] = Integer.parseInt(two[0]);
            interest[count] = Integer.parseInt(two[1]);
            sum[count] = school[count] + interest[count];
        }
    }

    Three get(int day) {
        return new Three(sum[day], school[day], interest[day]);
    }

    static class Three {
        int sum, school, interest;

        public Three(int sum, int school, int interest) {
            this.sum = sum;
            this.school = school;
            this.interest = interest;
        }
    }
}