ans=0
x=0
for i in range(int(input())):
a,b=map(int,input().split())
x=x-a
ans=max(ans,x)
x=x+b
ans=max(ans,x)
print(ans)#include<bits/stdc++.h>
#include <iostream>
#include <cstring>
#include <string>
#include <cmath>
#include <vector>
#include <utility>
#include <set>
using namespace std;
int main()
{long long b ;
cin >> b ;
long long n[b] ,m[b] , s = 0, d[b] , v=0;
for(int i = 0 ; i < b ; i++)
{
cin >> n[i] >> m[i];
s+= m[i];
s+= - n[i];
d[i]= s;
if(v < d[i])
{
v = d[i];
}
}
cout << v << endl;
return 0;}
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