#include <fstream>
using namespace std;
int main()
{
	int n, minoff, nextA, nextB, i, flag = 0, maxvalue = 0, linshi;
	ifstream fin("goz.in");
	ofstream fout("goz.out");
	fin >> n;
	fin >> nextA;
	fin >> nextB;
	if(nextA >= nextB)
	{
		flag = 1;
		maxvalue += nextA;
	}
	else
	{
		maxvalue += nextB;
	}
	minoff = nextA-nextB;
	for(i = 1; i < n; i++)
	{
		fin >> nextA;
		fin >> nextB;
		if(nextA >= nextB)
		{
			flag = 1;
			maxvalue += nextA;
		}
		else
		{
			maxvalue += nextB;
			linshi = nextA-nextB;
		}
		if(linshi > minoff)
		{
			minoff = linshi;
		}
	}
	if(flag = 0)
	{
		fout << maxvalue+minoff;
	}
	else
	{
		fout << maxvalue;
	}
	fin.close();
	fout.close();
	return 0;
}