#include <stdio.h>
#include <string.h>
int a[1000001],b[1000001],res[1000001],ind=0;
main()
{
int N,i;
memset (res,0,sizeof(res));
scanf("%d",&N);
for (i=0;i<N;i++)
    scanf("%d%d",&a[i],&b[i]);
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--)
        printf("%d",res[i]);
}