#include <cstdio>
#include <algorithm>

using namespace std;

struct pac {int l,d;};
pac a[100001];
int m[100001],n,i;
int main()
{FILE *f1 = fopen("pachete.in","r");
FILE *f2 = fopen("pachete.out","w");
fscanf(f1,"%d",&n);
for (i=1;i<=n;i++) fscanf(f1,"%d%d",&a[i].l,&a[i].d);
m[n]=a[n].d;
for (i=n-1;i>=1;i--) m[i]=a[i].d+max(0,m[i+1]-a[i].l);
fprintf(f2,"%d\n",m[1]);
fclose(f1);fclose(f2);
    return 0;
}