116A

#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;
}