#include <stdio.h>
#include <string.h>

int main()
{
 long i, N;
 int x, y;
 int mas[100], uk=0, s;

 freopen("1048.in", "r", stdin);
 freopen("1048.out", "w", stdout);

 memset(mas, 0, sizeof(mas));

 scanf("%ld", &N);

 scanf("%d%d", &x, &y);

 s=x+y;
 if (s > 10)
    {
     mas[uk]=s/10;
     mas[++uk]=s%10;
    }
  else mas[uk]=s;

 for (i=1; i<N; i++)
     {
      scanf("%d%d", &x, &y);

      s=x+y;
      if (s >= 10)
         {
          if (mas[uk] < 9)
             {
              mas[uk]+=s/10;
              mas[++uk]=s%10;
             }
           else
            {
             int p=uk;

             for (; p;)
                 {
                  if (mas[p] >= 9)
                     mas[p]=0;
                   else break;
                  p--;
                 }
             mas[p]+=s/10;
             mas[++uk]=s%10;
            }
         }
       else mas[++uk]=s;

      if (uk >= 99)
         {
          uk=1;
          printf("%d", mas[0]);
          for (int i=1; i<100; i++)
              mas[i-1]=mas[i];
         }
     }

 for (int i=0; i<=uk; i++)
     printf("%d", mas[i]);

 fclose(stdin);
 fclose(stdout);

 return 0;
}