#include <bits/stdc++.h>
using namespace std;
#define GG ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int main () { GG;
int n,c=0,mx=0,a,b; cin>>n;
for(int i=0;i<n;i++)
{ cin>>a>>b;
c+=-a+b;
mx=max(mx,c);
}
cout<<mx<<"\n";
return 0;}
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