import java.util.Scanner;

public class _1048 {
    public static void main(String[] args) throws Exception {
        Scanner s = new Scanner(System.in);
        int n, ind, i;
        n = s.nextInt();
        int[] a = new int[n];
        int[] b = new int[n];
        int[] res = new int[n];

        for (i = 0; i < n; i++) {
            a[i] = s.nextInt();
            b[i] = s.nextInt();
        }

        for (i = n - 1; i >= 1; i--) {
            ind = (a[i] + b[i]) / 10;
            if (ind > 0) {
                res[n - i] = ind;
                res[n - i - 1] += (a[i] + b[i]) % 10;
            } else
                res[n - 1 - i] += a[i] + b[i];

            if (res[n - i - 1] >= 10) {
                res[n - i] += res[n - i - 1] / 10;
                res[n - i - 1] = res[n - i - 1] % 10;
            }
        }
        res[n - 1] += a[0] + b[0];
        for (i = n - 1; i > -1; i--)
            System.out.print(res[i]);
    }
}