# include <vector>
# include <stdio.h>
# include <string.h>
# include <iostream>
# include <algorithm>
// # include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
const int M = 5e5 + 10;
const int mod = 1e9+7;

# define RG register
# define ST static

int n, a[M], b[M], m, deg[M];
vector<int> ps;
int fa[M], mx[M];
bool hv[M];
inline int getf(int x) {
    return fa[x] == x ? x : fa[x] = getf(fa[x]);
}

int main() {
    cin >> n;
    for (int i=1; i<=n; ++i) {
        scanf("%d%d", &a[i], &b[i]);
        ps.push_back(a[i]);
        ps.push_back(b[i]);
    }
    sort(ps.begin(), ps.end());
    ps.erase(unique(ps.begin(), ps.end()), ps.end());
    for (int i=1; i<=n; ++i) {
        a[i] = lower_bound(ps.begin(), ps.end(), a[i]) - ps.begin() + 1;
        b[i] = lower_bound(ps.begin(), ps.end(), b[i]) - ps.begin() + 1;
//        cout << a[i] << ‘ ‘ << b[i] << endl;
    }
    m = ps.size();
    for (int i=1; i<=m; ++i) fa[i] = i, hv[i] = 0, mx[i] = i;
    for (int i=1; i<=n; ++i) {
        deg[a[i]] ++, deg[b[i]] ++;
        int fu = getf(a[i]), fv = getf(b[i]);
        if(fu == fv) hv[fu] = 1;
        else {
            fa[fu] = fv;
            hv[fv] |= hv[fu];
            mx[fv] = max(mx[fv], mx[fu]);
        }
    }
    
    ll ans = 0;
    for (int i=1; i<=m; ++i) {
        ans += 1ll * (deg[i] - 1) * ps[i-1];
        if(fa[i] == i && !hv[i]) ans += ps[mx[i]-1];
    }
    cout << ans << endl;

    return 0;
}