#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

const ll INF = LLONG_MAX / 3;

void solve() {
    int N;
    cin >> N;
    vll cur(3, INF), nex(3);
    cur[0] = 0;
    rep(i, N) {
        fill(all(nex), INF);
        int cost, fee;
        cin >> cost >> fee;
        smin(nex[1], cur[0] + cost);
        smin(nex[2], cur[0] + cost * 2);
        smin(nex[1], cur[1] + cost + fee);
        smin(nex[2], cur[1] + cost * 2 + fee);
        smin(nex[2], cur[2] + cost + fee);
        smin(nex[0], nex[2]);
        swap(cur, nex);
    }
    cout << cur[0] << endl;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}