using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Ural {
    public class Prob1048 {
        private List<int> nums = new List<int>();
        int c = 0, cur = 0;

        private void AddNum(int v) {
            if (cur >= c) {
                nums.Add(v);
                c++; cur++;
            } else {
                nums[cur] = v;
                cur++;
            }

            if (v > 9) {
                for (int i = cur - 1; i > 0; i--) {
                    nums[i - 1]++;
                    nums[i] -= 10;
                    if (nums[i - 1] < 10)
                        break;
                }
            }
        }

        public void Run() {
            int N = Int32.Parse(Console.ReadLine());

            string[] tokens = Console.ReadLine().Split(new char[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries);
            int sum = Int32.Parse(tokens[0]) + Int32.Parse(tokens[1]);
            AddNum(sum);

            for (int i = 1; i < N; i++) {
                tokens = Console.ReadLine().Split(new char[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries);
                sum=Int32.Parse(tokens[0]) + Int32.Parse(tokens[1]);
                if (sum < 9) {
                    for (int j = 0; j < cur; j++) {
                        Console.Write(nums[j]);
                    }
                    cur = 0;
                }
                AddNum(sum);
            }

            for (int i = 0; i < cur; i++) {
                Console.Write(nums[i]);
            }

        }

        static void Main(string[] args) {
            new Prob1048().Run();
        }
    }
}