#include <iostream>
#include <algorithm>
using namespace std;
int main() {
int a,n,b[1000][2],s[1000],i,j,max=-1000000;
cin>>n;
for(i=1;i<=n;i++){
for(j=0;j<=1;j++){
cin>>b[i][j];
}
}
s[1]=b[1][1];
for(i=2;i<=n-1;i++){
s[i]=s[i-1]+b[i][1]-b[i][0];
}
for(i=1;i<=n-1;i++){
if(max<s[i]) max=s[i];
}
printf("%d",max);
}
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