#include<stdio.h>
int main()
{
    int n,a,b,c,d,i,j,count,sum,sum1,x[1001],largest,k;
    scanf("%d", &n);
    scanf("%d %d", &c, &d);
    sum1=d-c;
    x[0] = sum1;
    for(i=0; i<n-1; i++){
        scanf("%d %d", &a, &b);
        sum1 = (sum1-a)+b;
        x[i+1] = sum1;
    }

    largest = x[0];


    for(j=1; j<n; j++){
        if(largest < x[j]){
            largest = x[j];
        }
    }
    printf("%d\n", largest);

}