#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int main() {
int ans = 0;
int tot = 0;
int n, a, b;
cin >> n;
for(int i = 0; i < n; ++i) {
cin >> a >> b;
tot -= a;
tot += b;
ans = max(ans, tot);
}
cout << ans << endl;
return 0;
}