#include <stdio.h>
#include <stdlib.h>

#define ONLINE_CONTEST
void main()
{
    long n;
    long nr;
    int i, x, y, ant, first = 1;
#ifndef ONLINE_CONTEST
    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
#endif
    scanf("%ld", &n);
    nr  = 0;
    for(i = 0; i < n; i++)
    {
        scanf("%d%d", &x, &y);
        x = x + y;
        if(first)
        {
            first = 0;
            ant = x;
        }
        else if(x < 9)
        {
            printf("%d", ant);
            for(y = 0; y < nr;y++)
            {
                printf("9");
            }
            ant = x;
            nr=0;
        }
        else if(x == 9)
        {
            nr++;
        }
        else if(x > 9)
        {
            printf("%d", ant+1);
            for(y = 0; y < nr; y++)
            {
                printf("0");
            }
            ant = x % 10;
            nr = 0;
        }
    }
    if(!first)
        printf("%d", ant);
}