//#ifndef khos
//#pragma GCC optimize ("Ofast")
//#pragma GCC optimize ("unroll-loops")
//#endif
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#ifdef khos
#include "t_debug.cpp"
#else
#define debug(...) 42
#endif
using namespace std;
using namespace __gnu_pbds;
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> using indexed_multiset = tree<pair<int,int>, null_type, less<pair<int,int>>, rb_tree_tag, tree_order_statistics_node_update>;
#define int int64_t
#define vi vector
#define ss second
#define ff first
#define TESTCASES
#define all(x) (x).begin(), (x).end()
const int mod = 1e9+7;
const int MAXN=2000000+5;
const int inf=1e18;
void solution() {
int n;
cin >> n;
vi<int> a(n), b(n);
vi<pair<int,int>> p;
for(int i=0; i<n; i++){
cin >> a[i] >> b[i];
p.push_back({a[i], b[i]});
}
sort(all(p));
int mx=-inf;
for(int i=0; i<n; i++){
int sum=0;
for(int j=i; j<n; j++){
sum+=p[j].ss;
mx=max(mx, sum-p[j].ff+p[i].ff);
}
}
cout << mx;
}
int32_t main(){
clock_t tStart = clock();
#ifdef khos
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
std::ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int q = 1;
#ifdef TESTCASES
// cin >> q;
#endif
while(q--) {
solution();
cout << '\n';
}
cerr<<fixed<<setprecision(3)<<"\nTime Taken: "<<(double)(clock()- tStart)/CLOCKS_PER_SEC<<endl;
}
