#include <bits/stdc++.h>
#define ff first
#define ss second
using namespace std;
typedef long long ll;
typedef pair<ll, ll> ii;
const int maxn = 500010;
const ll inf = 0x3f3f3f3f3f3f3f3f;
ll p[maxn];
ii v[maxn];
ll a[maxn];
ll b[maxn];
ll s[maxn];
inline ll scan () {
ll result = 0;
char ch;
ch = getchar_unlocked();
while (true) {
if (ch >= '0' && ch <= '9') break;
ch = getchar_unlocked();
}
result = ch-'0';
while (true) {
ch = getchar_unlocked();
if (ch < '0' || ch > '9') break;
result = result*10ll + (ch - '0');
}
return result;
}
int main()
{
int n = scan();
for (int i = 1; i <= n; i++) v[i].ff = scan(), v[i].ss = scan();
sort(v+1, v+1+n);
for (int i = 1; i <= n; i++) p[i] = p[i-1] + v[i].ss;
for (int i = 1; i <= n; i++) a[i] = -p[i-1] + v[i].ff;
for (int i = 1; i <= n; i++) b[i] = p[i]-v[i].ff;
s[n+1] = -inf;
for (int i = n; i >= 1; i--) s[i] = max(s[i+1], b[i]);
ll ans = -inf;
for (int i = 1; i <= n; i++) ans = max(ans, a[i]+s[i]);
printf("%lld\n", ans);
}
