#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll, ll>
#define fi first
#define se second
inline ll in() {
ll result = 0;
char ch = getchar_unlocked();
while(true) {
if(ch >= '0' && ch <= '9')
break;
ch = getchar_unlocked();
}
result = ch-'0';
while(true) {
ch = getchar_unlocked();
if (ch < '0' || ch > '9')
break;
result = result*10 + (ch - '0');
}
return result;
}
inline void out(ll x) {
ll rev=x;
int c=0;
while(!(rev%10)) {
++c;
rev/=10;
}
rev=0;
while(x) {
rev=rev*10+x%10;
x/=10;
}
while(rev) {
putchar_unlocked(rev%10+'0');
rev/=10;
}
while(c--)
putchar_unlocked('0');
}
const int mxN=5e5;
int n;
ll mx, ans;
pll ps[mxN+1];
int main() {
n=in();
for(int i=1; i<=n; ++i)
ps[i].fi=in(), ps[i].se=in();
sort(ps, ps+n+1);
for(int i=1; i<=n; ++i) {
ps[i].se+=ps[i-1].se;
mx=max(ps[i].fi-ps[i-1].se, mx);
ans=max(ps[i].se-ps[i].fi+mx, ans);
}
out(ans);
}
