#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < (n); i++)
#define repr(i, n) for (int i = (n) - 1; i >= 0; i--)

using namespace std;
using ll = long long;

void chmin(ll &x, ll y) {
  x = min(x, y);
}

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int N; cin >> N;
  vector<ll> C(N + 1), D(N + 1); rep(i, N) cin >> C[i] >> D[i];
  const ll INF = 1e18;
  vector<ll> dp(N + 1, INF);
  vector<ll> ep(N + 1, INF);
  dp[0] = -D[0];
  rep(i, N) {
    chmin(dp[i + 1], dp[i] - D[i + 1] + C[i]);
    chmin(dp[i + 1], dp[i]);
    chmin(ep[i + 1], dp[i] + C[i]);
    chmin(ep[i + 1], ep[i]);
    chmin(dp[i + 1], ep[i] - D[i + 1]);
  }
  ll sumc = 0, sumd = 0;
  rep(i, N) sumc += C[i], sumd += D[i];
  cout << ep[N] + sumc + sumd << endl;
}