#include <bits/stdc++.h>
#define int long long
#define iamaperson int main() {\
preprocess();\
int t = 1; while (t--) solve();\
}
using namespace std;
int INF = 9e18+23;
void preprocess() {} // just in case!!!!1
void solve() {
int n; cin >> n;
vector<array<int, 2>> x(n); for (auto &[a, b] : x) cin >> a >> b;
vector<array<int, 2>> dp(1+n, {-INF-1, -INF-1});
sort(x.begin(), x.end());
dp[n][0] = -INF;
dp[n][1] = 0;
for (int i = n-1; i >= 0; --i) {
if (i != n-1) {
dp[i][0] = max(dp[i][0], dp[i+1][1]+x[i][0]+x[i][1]);
dp[i][1] = max(dp[i][1], dp[i+1][1]+x[i][1]);
}
dp[i][0] = max(dp[i][0], dp[i+1][0]);
dp[i][0] = max(dp[i][0], x[i][1]);
dp[i][1] = max(dp[i][1], x[i][1]-x[i][0]);
}
cout << dp[0][0];
}
#undef int
iamaperson
