#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define ll long long
#define ld long double
#define all(_v) _v.begin(), _v.end()
#define sz(_v) (int)_v.size()
#define pii pair <int, int>
#define pll pair <ll, ll>
#define veci vector <int>
#define vecll vector <ll>
const int dx[4] = {1, -1, 0, 0};
const int dy[4] = {0, 0, -1, 1};
const double PI = 3.1415926535897932384626433832795;
const double eps = 1e-9;
const int MOD1 = 1e9 + 7;
const int MOD2 = 998244353;
/**
a1 > a2
b1 - a1 < b1 + b2 - a1 + a2
-a1 < b2 - a1 + a2
0 < b2 + a2
a1 < a2
b1 - a1 < b1 + b2 - a2 + a1
-a1 < -a2 + a1 + b2
-2*a1 < b2 - a2
2a1 > a2 - b2
**/
const int MAXN = 2e5 + 10;
int n;
ll a[MAXN], b[MAXN];
int ord[MAXN];
bool cmp(int i, int j) {
return (b[i] - a[i] < b[j] - a[j]);
}
void solve() {
cin >> n;
for(int i = 1; i <= n; ++i)
cin >> a[i] >> b[i];
if(n <= 16) {
ll ans = 0;
for(int mask = 0; mask < (1 << n); ++mask) {
ll s = 0;
ll mx = -1e18, mn = 1e18;
for(int i = 0; i < n; ++i) {
if((mask >> i) & 1) {
s += b[i + 1];
mx = max(mx, a[i + 1]);
mn = min(mn, a[i + 1]);
}
}
ans = max(ans, s - (mx - mn));
}
cout << ans;
exit(0);
}
for(int i = 1; i <= n; ++i)
ord[i] = i;
sort(ord + 1, ord + n + 1, &cmp);
ll ans = 0;
ll s = 0;
ll mn = 1e18, mx = -1e18;
for(int i = n; i > 0; --i) {
mn = min(mn, a[ord[i]]);
mx = max(mx, a[ord[i]]);
s += b[ord[i]];
ans = max(ans, s - (mx - mn));
}
s = 0;
mn = 1e18, mx = -1e18;
for(int i = 1; i <= n; ++i) {
mn = min(mn, a[ord[i]]);
mx = max(mx, a[ord[i]]);
s += b[ord[i]];
ans = max(ans, s - (mx - mn));
}
cout << ans;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int T = 1;
///cin >> T;
while(T--) solve(), cout << '\n';
return 0;
}
