#include <iostream>
#include <algorithm>
using namespace std;
long long* X;
long long* Y;
bool f(long long a, long long b)
{
return X[a] < X[b];
}
int main()
{
long long N;
cin >> N;
X = new long long[N+1];
Y = new long long[N+1];
long long A[N+1], B[N+1];
for(long long i = 1; i <= N; i++) cin >> X[i] >> Y[i];
long long I[N+1];
for(long long i = 0; i <= N; i++) I[i] = i;
sort(I+1, I+N+1, f);
long long a = 1;
for(long long i:I)
{
if(i == 0) continue;
A[a] = X[i];
B[a] = Y[i];
a++;
}
for(long long i = 2; i <= N; i++) B[i] += B[i-1];
A[0] = B[0] = 0;
for(long long i = 1; i <= N; i++)
{
X[i] = A[i] - B[i-1];
Y[i] = B[i] - A[i];
}
for(long long i = N-1; i >= 1; i--) Y[i] = max(Y[i], Y[i+1]);
long long res = 0;
for(long long i = 1; i <= N; i++) res = max(res, X[i] + Y[i]);
cout << res << '\n';
return 0;
}
