#include <bits/stdc++.h>
using namespace std;
#define X first
#define Y second
#define mp make_pair
#define pb push_back
#define Debug(...) fprintf(stderr, __VA_ARGS__)
typedef long long LL;
typedef long double LD;
typedef unsigned int uint;
typedef pair <int, int> pii;
typedef unsigned long long uLL;
template <typename T> inline void Read(T &x) {
char c = getchar();
bool f = false;
for (x = 0; !isdigit(c); c = getchar()) {
if (c == '-') {
f = true;
}
}
for (; isdigit(c); c = getchar()) {
x = x * 10 + c - '0';
}
if (f) {
x = -x;
}
}
template <typename T> inline bool CheckMax(T &a, const T &b) {
return a < b ? a = b, true : false;
}
template <typename T> inline bool CheckMin(T &a, const T &b) {
return a > b ? a = b, true : false;
}
const int N = 500005;
LL ans, val, a[N], b[N];
int n, p[N];
int main() {
#ifdef wxh010910
freopen("d.in", "r", stdin);
#endif
Read(n);
for (int i = 1; i <= n; ++i) {
Read(a[i]), Read(b[i]), p[i] = i;
}
sort(p + 1, p + n + 1, [&](const int &x, const int &y) {
return a[x] < a[y];
});
for (int i = 1; i <= n; ++i) {
b[p[i]] += b[p[i - 1]];
CheckMax(val, a[p[i]] - b[p[i - 1]]);
CheckMax(ans, val + b[p[i]] - a[p[i]]);
}
printf("%lld\n", ans);
#ifdef wxh010910
Debug("My Time: %.3lfms\n", (double)clock() / CLOCKS_PER_SEC);
#endif
return 0;
}
