#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2e5 + 5;
template <typename T>
void chkmax(T &x, T y) {
  x = max(x, y);
}
template <typename T>
void chkmin(T &x, T y) {
  x = min(x, y);
}
template <typename T>
void read(T &x) {
  x = 0;
  int f = 1;
  char c = getchar();
  for (; !isdigit(c); c = getchar())
    if (c == '-') f = -f;
  for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
  x *= f;
}
template <typename T>
void write(T x) {
  if (x < 0) x = -x, putchar('-');
  if (x > 9) write(x / 10);
  putchar(x % 10 + '0');
}
template <typename T>
void writeln(T x) {
  write(x);
  puts("");
}
int a[MAXN], b[MAXN];
int main() {
  int n;
  read(n);
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    read(a[i]), read(b[i]);
    ans += 1 + a[i] + b[i];
  }
  sort(a + 1, a + n + 1);
  sort(b + 1, b + n + 1);
  for (int i = 1; i <= n; i++) ans -= min(a[i], b[i]);
  writeln(ans);
  return 0;
}
