#include <stdio.h>
int main()
{
int n;
int a1,a2;
int min=0;
int cap=0;
scanf("%d",&n);
while(n>0)
{
scanf("%d %d",&a1,&a2);
cap-=a1;
cap+=a2;
if(min<cap)
min=cap;
--n;
}
printf("%d\n",min);
return 0;
}