import java.util.*;

public class Main {
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	PriorityQueue<Path> queue = new PriorityQueue<>();
    	long total = 0;
    	int first = sc.nextInt();
    	total += first;
    	queue.add(new Path(0, n, first));
    	sc.nextInt();
    	for (int i = 1; i < n; i++) {
    	    int each = sc.nextInt();
    	    total += each;
    	    queue.add(new Path(i, n, each));
    	    queue.add(new Path(i - 1, i, sc.nextInt()));
    	}
    	UnionFindTree uft = new UnionFindTree(n + 1);
    	while (queue.size() > 0) {
    	    Path p = queue.poll();
    	    if (!uft.same(p)) {
    	        uft.unite(p);
    	        total += p.cost;
    	    }
    	}
    	System.out.println(total);
    }
    
    static class UnionFindTree {
        int[] parents;
        
        public UnionFindTree(int size) {
            parents = new int[size];
            for (int i = 0; i < size; i++) {
                parents[i] = i;
            }
        }
        
        public int find(int x) {
            if (x == parents[x]) {
                return x;
            } else {
                return parents[x] = find(parents[x]);
            }
        }
        
        public boolean same(int x, int y) {
            return find(x) == find(y);
        }
        
        public boolean same(Path p) {
            return same(p.left, p.right);
        }
        
        public void unite(int x, int y) {
            if (!same(x, y)) {
                parents[find(x)] = find(y);
            }
        }
        
        public void unite(Path p) {
            unite(p.left, p.right);
        }
    }
    static class Path implements Comparable<Path> {
        int left;
        int right;
        int cost;
        
        public Path(int left, int right, int cost) {
            this.left = left;
            this.right = right;
            this.cost = cost;
        }
        
        public int compareTo(Path another) {
            return cost - another.cost;
        }
    }
}