A. Tram Solution

#include<bits/stdc++.h>

using namespace std;

int main(){

    int a,n,enter1=0,exit1=0,enter2=0,exit2=0,pass;

    cin >> a;

    n=a-1;

    int max=0;

    cin>>exit1>>enter1;

    if(max<enter1)

        max=enter1;

    while(n>0){

        cin>>exit2>>enter2;

        n=n-1;

        pass=enter1-exit2+enter2;

        enter1=enter1-exit2+enter2;

        if (pass>max)

            max=pass;

    }

    cout<<max<<endl;

    return 0;

}