#include <bits/stdc++.h>
using namespace std;
#define USE_STD_IO 1
#if USE_STD_IO
#define fin cin
#define fout cout
#else
ifstream fin(".in");
ofstream fout(".out");
#endif
struct Tablou {
long long mar, val;
} v[500002];
long long n, i, val, ma, rasp;
static inline bool Cmp(Tablou t1, Tablou t2) {
return t1.mar < t2.mar;
}
int main() {
if(USE_STD_IO) ios_base::sync_with_stdio(false);
fin.tie(NULL);
fout.tie(NULL);
fin >> n;
for(i = 1; i <= n; i++) {
fin >> v[i].mar >> v[i].val;
}
sort(v + 1, v + n + 1, Cmp);
for(i = 1; i <= n; i++) {
ma = max(ma, v[i].mar - val);
val += v[i].val;
rasp = max(rasp, ma + val - v[i].mar);
}
fout << rasp;
return 0;
}
