#include <bits/stdc++.h>
using namespace std;
int main()
{
int n;
cin >> n;
int sumL = 0, bestGain = 0;
for (int i = 0; i < n; i++)
{
int l, r;
cin >> l >> r;
sumL += l;
bestGain = max(bestGain, r - l);
}
cout << sumL + bestGain << '\n';
return 0;
}
