import java.util.Arrays;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.OutputStream;
public class art {
private static class Kattio extends PrintWriter {
public Kattio(InputStream i) {
super(new BufferedOutputStream(System.out));
r = new BufferedReader(new InputStreamReader(i));
}
public Kattio(InputStream i, OutputStream o) {
super(new BufferedOutputStream(o));
r = new BufferedReader(new InputStreamReader(i));
}
public boolean hasMoreTokens() {
return peekToken() != null;
}
public int getInt() {
return Integer.parseInt(nextToken());
}
public double getDouble() {
return Double.parseDouble(nextToken());
}
public long getLong() {
return Long.parseLong(nextToken());
}
public String getWord() {
return nextToken();
}
private BufferedReader r;
private String line;
private StringTokenizer st;
private String token;
private String peekToken() {
if (token == null)
try {
while (st == null || !st.hasMoreTokens()) {
line = r.readLine();
if (line == null)
return null;
st = new StringTokenizer(line);
}
token = st.nextToken();
} catch (IOException e) {
}
return token;
}
private String nextToken() {
String ans = peekToken();
token = null;
return ans;
}
}
private static class Reader {
final private int BUFFER_SIZE = 1 << 16;
private DataInputStream din;
private byte[] buffer;
private int bufferPointer, bytesRead;
public Reader()
{
din = new DataInputStream(System.in);
buffer = new byte[BUFFER_SIZE];
bufferPointer = bytesRead = 0;
}
public Reader(String file_name) throws IOException
{
din = new DataInputStream(
new FileInputStream(file_name));
buffer = new byte[BUFFER_SIZE];
bufferPointer = bytesRead = 0;
}
public String readLine() throws IOException
{
byte[] buf = new byte[64]; // line length
int cnt = 0, c;
while ((c = read()) != -1) {
if (c == '\n') {
if (cnt != 0) {
break;
}
else {
continue;
}
}
buf[cnt++] = (byte)c;
}
return new String(buf, 0, cnt);
}
public int nextInt() throws IOException
{
int ret = 0;
byte c = read();
while (c <= ' ') {
c = read();
}
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (neg)
return -ret;
return ret;
}
public long nextLong() throws IOException
{
long ret = 0;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (neg)
return -ret;
return ret;
}
public double nextDouble() throws IOException
{
double ret = 0, div = 1;
byte c = read();
while (c <= ' ')
c = read();
boolean neg = (c == '-');
if (neg)
c = read();
do {
ret = ret * 10 + c - '0';
} while ((c = read()) >= '0' && c <= '9');
if (c == '.') {
while ((c = read()) >= '0' && c <= '9') {
ret += (c - '0') / (div *= 10);
}
}
if (neg)
return -ret;
return ret;
}
private void fillBuffer() throws IOException
{
bytesRead = din.read(buffer, bufferPointer = 0,
BUFFER_SIZE);
if (bytesRead == -1)
buffer[0] = -1;
}
private byte read() throws IOException
{
if (bufferPointer == bytesRead)
fillBuffer();
return buffer[bufferPointer++];
}
public void close() throws IOException
{
if (din == null)
return;
din.close();
}
}
private static final class Artwork {
public final long a;
public final int b;
public Artwork(long a, int b) {
this.a = a;
this.b = b;
}
}
private static int clamp(long x) {
if (x < 0) return -1;
if (x > 0) return 1;
return 0;
}
public static void main(String[] args) throws IOException {
Reader io = new Reader();
int n = io.nextInt();
Artwork[] artworks = new Artwork[n];
for (int i=0; i<n; ++i) {
artworks[i] = new Artwork(io.nextLong(), io.nextInt());
}
Arrays.sort(artworks, (t, o) -> clamp(t.a - o.a));
long[] f = new long[n+1];
f[0] = 0;
long minSoFar = (long) 4e18;
long result = 0;
long prev = 0;
for (int i=0; i<n; ++i) {
long cur = prev + artworks[i].b;
result = Math.max(result, artworks[i].b);
long tmp = cur - artworks[i].a;
result = Math.max(result, tmp - minSoFar);
minSoFar = Math.min(minSoFar, prev - artworks[i].a);
prev = cur;
}
System.out.println(result);
}
}
