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{ 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());} } }