#include <bits/stdc++.h>
using namespace std;
using ll = long long;
struct SegTree_sum {
vector<ll> values;
int base;
SegTree_sum(vector<ll>& vec) {
base = 1;
while (base <= vec.size()) base *= 2;
values.assign(base * 2, 0);
for (int i=0; i<vec.size(); i++) values[base + i] = vec[i];
for (int i=base-1; i>=1; i--) values[i] = values[i*2] + values[i*2+1];
}
ll Query(int l, int r) {
l += base - 1;
r += base + 1;
ll ans = 0;
while (l/2 != r/2) {
if (l%2 == 0) ans += values[l+1];
if (r%2 != 0) ans += values[r-1];
l /= 2, r /= 2;
}
return ans;
}
};
struct SegTree_max {
vector<ll> values;
int base;
SegTree_max(vector<ll>& vec) {
base = 1;
while (base <= vec.size()) base *= 2;
values.assign(base * 2, LLONG_MIN);
for (int i=0; i<vec.size(); i++) values[base + i] = vec[i];
for (int i=base-1; i>=1; i--) values[i] = max(values[i*2], values[i*2+1]);
}
ll Query(int l, int r) {
l += base - 1;
r += base + 1;
ll ans = LLONG_MIN;
while (l/2 != r/2) {
if (l%2 == 0) ans = max(ans, values[l+1]);
if (r%2 != 0) ans = max(ans, values[r-1]);
l /= 2, r /= 2;
}
return ans;
}
};
struct SegTree_min {
vector<ll> values;
int base;
SegTree_min(vector<ll>& vec) {
base = 1;
while (base <= vec.size()) base *= 2;
values.assign(base * 2, LLONG_MAX);
for (int i=0; i<vec.size(); i++) values[base + i] = vec[i];
for (int i=base-1; i>=1; i--) values[i] = min(values[i*2], values[i*2+1]);
}
ll Query(int l, int r) {
l += base - 1;
r += base + 1;
ll ans = LLONG_MAX;
while (l/2 != r/2) {
if (l%2 == 0) ans = min(ans, values[l+1]);
if (r%2 != 0) ans = min(ans, values[r-1]);
l /= 2, r /= 2;
}
return ans;
}
};
int N; // liczba dzieł sztuki
vector<ll> art_size;
vector<ll> art_value;
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> N;
art_size.assign(N, 0);
art_value.assign(N, 0);
vector<pair<ll,ll>> vec;
for (int i=0; i<N; i++) {
cin >> art_size[i] >> art_value[i];
vec.push_back({ art_size[i], art_value[i] });
}
sort(vec.begin(), vec.end());
for (int i=0; i<N; i++) {
art_size[i] = vec[i].first;
art_value[i] = vec[i].second;
}
SegTree_sum sums(art_value);
SegTree_max maxs(art_size);
SegTree_min mins(art_size);
ll ans = art_value[0];
for (int i=0; i<N; i++) for (int j=i; j<N; j++) {
ll SUM = sums.Query(i,j);
ll MAX = maxs.Query(i,j);
ll MIN = mins.Query(i,j);
ans = max(ans, SUM - (MAX - MIN));
}
cout << ans << '\n';
}
