#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <cmath>
#include <vector>
#include <stack>
#include <cstdlib>
#include <queue>
#include <map>
#include <math.h>
#include <list>
#include <set>

using namespace std;

struct numl
{
	vector <int> num;
	numl() : num() {};
	numl(vector <int> _num) : num(_num) {};
	numl operator + (numl v)
	{
		numl sum;
		int counter = 0;
		if (num.size() >= v.num.size())
		{
			int n = num.size()-1;
			for (int i = v.num.size()-1; i >= 0; i--)
			{
				if (num[n] + v.num[i] + counter > 9)
				{
					sum.num.push_back((num[n] + v.num[i] + counter)%10);
					counter = (num[n] + v.num[i] + counter)/10;
				}
				else
				{
					sum.num.push_back(num[n] + v.num[i] + counter);
					counter = 0;
				}
				n--;
			}
			while (n >= 0)
			{
				if (num[n] + counter > 9)
				{
					sum.num.push_back((num[n] + counter) % 10);
					counter = (num[n] + counter)/10;
				}
				else
				{
					sum.num.push_back(num[n] + counter);
					counter = 0;
				}
				n--;
			}
		}
		else
		{
			int n = v.num.size()-1;
			for (int i = num.size()-1; i >= 0; i--)
			{
				if (num[i] + v.num[n] + counter > 9)
				{
					sum.num.push_back((num[i] + v.num[n] + counter)%10);
					counter = (num[i] + v.num[n] + counter)/10;
				}
				else
				{
					sum.num.push_back(num[i] + v.num[n] + counter);
					counter = 0;
				}
				n--;
			}
			while (n >= 0)
			{
				if (v.num[n] + counter > 9)
				{
					sum.num.push_back((v.num[n] + counter) % 10);
					counter = (v.num[n] + counter)/10;
				}
				else
				{
					sum.num.push_back(v.num[n] + counter);
					counter = 0;
				}
				n--;
			}
		}
		if (counter > 0)
			sum.num.push_back(counter);
		return sum;
	}
} num1, num2, ans;

int n;

int main()
{
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
	scanf("%d", &n);
	for (int i = 0; i < n; i++)
	{
		int k, p;
		scanf("%d%d", &k, &p);
		if (k != 0 || !num1.num.empty())
			num1.num.push_back(k);
		if (p != 0 || !num2.num.empty())
			num2.num.push_back(p);
	}
	ans = num1 + num2;
	reverse(ans.num.begin(), ans.num.end());
	for (int i = 0; i < ans.num.size(); i++)
		printf("%d", ans.num[i]);
	return 0;
}