import java.util.*;
import java.io.*;

public class Main {
	public static long gcd(long n, long m){ if(m > n) return gcd(m,n); if(m == 0) return n; return gcd(m, n%m);}
	public static long lcm(long m, long n){ return (m/gcd(m,n))*n;}
	static int mod = 1000000007;
	static int INF = Integer.MAX_VALUE;
	static int[] dx = {0,0,1,-1};
	static int[] dy = {1,-1,0,0};
	static int[] dx8 = {0,0,1,-1,1,1,-1,-1};
	static int[] dy8 = {1,-1,0,0,1,-1,-1,1};
	public static void main(String[] args){
		FastScanner scanner = new FastScanner();
		int n = scanner.nextInt();
		long[] a = new long[2*n];
		for(int i = 0; i < 2*n; i++){
			a[i] = scanner.nextLong();
		}
		long[] evensum = new long[2*n];
		long[] oddsum = new long[2*n];
		for(int i = 0; i < 2*n; i++){
			if(i % 2 == 0){
				evensum[i] = a[i];
			}else{
				oddsum[i] = a[i];
			}
		}
		for(int i = 0; i < 2*n-1; i++){
			evensum[i+1] += evensum[i];
			oddsum[i+1] += oddsum[i];
		}
		long max = -Long.MAX_VALUE;
		for(int i = 0; i < 2*n; i++){
			if(i % 2 == 1){
				max = Math.max(max,evensum[i]-oddsum[i]-(evensum[2*n-1]-evensum[i])+oddsum[2*n-1]-oddsum[i]);
			}
		}
		System.out.println(max);
	}

	static class Pair implements Comparable<Pair>{
    int first, second;
    Pair(int a, int b){
        first = a;
        second = b;
    }
    @Override
    public boolean equals(Object o){
        if (this == o) return true;
        if (!(o instanceof Pair)) return false;
        Pair p = (Pair) o;
        return first == p.first && second == p.second;
    }
    @Override
    public int compareTo(Pair p){
        return first == p.first ? second - p.second : first - p.first; //firstで昇順にソート
        //return (first == p.first ? second - p.second : first - p.first) * -1; //firstで降順にソート
        //return second == p.second ? first - p.first : second - p.second;//secondで昇順にソート
        //return (second == p.second ? first - p.first : second - p.second)*-1;//secondで降順にソート
        //return first * 1.0 / second > p.first * 1.0 / p.second ? 1 : -1; // first/secondの昇順にソート
        //return first * 1.0 / second < p.first * 1.0 / p.second ? 1 : -1; // first/secondの降順にソート
        //return second * 1.0 / first > p.second * 1.0 / p.first ? 1 : -1; // second/firstの昇順にソート
        //return second * 1.0 / first < p.second * 1.0 / p.first ? 1 : -1; // second/firstの降順にソート
        //return Math.atan2(second, first) > Math.atan2(p.second, p.first) ? 1 : -1; // second/firstの昇順にソート
        //return first + second > p.first + p.second ? 1 : -1; //first+secondの昇順にソート
        //return first + second < p.first + p.second ? 1 : -1; //first+secondの降順にソート
        //return first - second < p.first - p.second ? 1 : -1; //first-secondの降順にソート
        //return second - first < p.second - p.first ? 1 : -1; //first-secondの昇順にソート
        //return second - first < p.second - p.first ? -1 : 1; //second-firstの昇順にソート
        //return Math.atan2(second,first) > Math.atan2(p.second, p.first) ? 1 : -1;
        //return Math.max(first,second)-Math.max(p.first,p.second);
    }
	}
	static class RMQ {
		private int size_, dat[];
		private int query_(int a, int b, int k, int l, int r) {
			if(r <= a || b <= l) return 2147483647;
			if(a <= l && r <= b) return dat[k];
			int lc = query_(a, b, 2 * k, l, (l + r) / 2);
			int rc = query_(a, b, 2 * k + 1, (l + r) / 2, r);
			return Math.min(lc, rc);
		}
		RMQ(int s) {
			for(size_ = 1; size_ < s;) size_ *= 2;
			dat = new int[size_ * 2];
			for(int i = 0; i < size_ * 2; i++) dat[i] = 2147483647;
		}
		public void update(int pos, int x) {
			pos += size_; dat[pos] = x;
			while(pos > 1) {
				pos /= 2;
				dat[pos] = Math.min(dat[2 * pos], dat[2 * pos + 1]);
			}
		}
		public int query(int l, int r) {
			return query_(l, r, 1, 0, size_);
		}
	}
	static int size = 2100000;
	static long[] fac = new long[size];
	static long[] finv = new long[size];
	static long[] inv = new long[size];
	//繰り返し二乗法
	public static long pow(long x, long n){
		long ans = 1;
		while(n > 0){
			if((n & 1) == 1){
				ans = ans * x;
				ans %= mod;
			}
			x = x * x % mod;
			n >>= 1;
		}
		return ans;
	}
	public static long div(long x, long y){
		return (x*pow(y, mod-2))%mod;
	}
	//fac, inv, finvテーブルの初期化、これ使う場合はinitComb()で初期化必要
	public static  void initComb(){
		fac[0] = finv[0] = inv[0] = fac[1] = finv[1] = inv[1] = 1;
		for (int i = 2; i < size; ++i) {
			fac[i] = fac[i - 1] * i % mod;
			inv[i] = mod - (mod / i) * inv[(int) (mod % i)] % mod;
			finv[i] = finv[i - 1] * inv[i] % mod;
		}
	}
	//nCk % mod
	public static long comb(int n, int k){
		return fac[n] * finv[k] % mod * finv[n - k] % mod;
	}
	//n! % mod
	public static long fact(int n){
		return fac[n];
	}
	//(n!)^-1 with % mod
	public static long finv(int n){
		return finv[n];
	}
	private static class FastScanner {
		private final InputStream in = System.in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;
		private boolean hasNextByte() {
				if (ptr < buflen) {
						return true;
				}else{
						ptr = 0;
						try {
								buflen = in.read(buffer);
						} catch (IOException e) {
								e.printStackTrace();
						}
						if (buflen <= 0) {
								return false;
						}
				}
				return true;
		}
		private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
		private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
		public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
		public String next() {
				if (!hasNext()) throw new NoSuchElementException();
				StringBuilder sb = new StringBuilder();
				int b = readByte();
				while(isPrintableChar(b)) {
						sb.appendCodePoint(b);
						b = readByte();
				}
				return sb.toString();
		}
		public long nextLong() {
				if (!hasNext()) throw new NoSuchElementException();
				long n = 0;
				boolean minus = false;
				int b = readByte();
				if (b == '-') {
						minus = true;
						b = readByte();
				}
				if (b < '0' || '9' < b) {
						throw new NumberFormatException();
				}
				while(true){
						if ('0' <= b && b <= '9') {
								n *= 10;
								n += b - '0';
						}else if(b == -1 || !isPrintableChar(b)){
								return minus ? -n : n;
						}else{
								throw new NumberFormatException();
						}
						b = readByte();
				}
		}
		public int nextInt() {
				long nl = nextLong();
				if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
				return (int) nl;
		}
		public double nextDouble() { return Double.parseDouble(next());}
	}
}