#include<iostream>
#include<fstream>

using namespace std;

ifstream fin("pachete.in");
ofstream fout("pachete.out");

#define MAX_N 100000
int inst[MAX_N], down[MAX_N], minim[MAX_N];
int n;

inline void read(){
	fin >> n;
	
	for(int i=1; i<=n; i++){
		fin >> inst[i] >> down[i];
	}
}


void solve(){
	minim[n] = down[n];
	
	for(int i=n-1; i>=1; i--){
		int maxim = 0;
		if(maxim < minim[i+1] - inst[i]) maxim = minim[i+1] - inst[i];
		minim[i] = down[i] + maxim;
	}
	
	fout << minim[1] << '\n';
	
}


int main(){

	read();
	solve();
	
return 0;
}