#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
int main()
{

vector<int> a,b,c;
int x=0,sum,val=0;
long int n;
int z,v;
do
{
cin>>n;
}while(n==0);

for(x=0;x<n;x++)
{
cin>>z>>v;
a.push_back(z);
b.push_back(v);
}
vector<int>::iterator i,j,k;
for(x=0,i=a.end(),j=b.end();x<n;x++)
{
i--;j--;
sum=(((*i)+(*j))%10)+val;
c.push_back(sum);
val = ((*i)+(*j))/10;
}

for(k=c.end();k!=c.begin();)
{
k--;
cout<<*k;
}

return 0;
}

On the test
3
1 1
9 0
9 1
Your program gives 2100
The right answer is 300.
Good Luck!

Thank You!!!
My solution was accepted.

to: AlexF
Thanks!