#include <iostream>
#include <cstring>
#include <vector>
#include <utility>
#include <algorithm>

using namespace std;

int n;
vector<pair<long long, long long>> item;
long long dp[100001];

long long dfs(int id){
    if(id == n){
        return 0;
    }
    if(~dp[id]) return dp[id];
    long long res = 1ll << 62, minItem = 1ll << 62;
    long long sum = 0;
    for(int i = id + 1; i <= n; i++){
        minItem = min(minItem, item[i - 1].first);
        if(i - id == 1){
            sum += item[i - 1].first;
        }else{
            sum += item[i - 1].first + item[i - 1].second;
        }
        res = min(res, sum + minItem + dfs(i));
    }
    return dp[id] = res;
}

int main(){
    cin >> n;
    item.resize(n);
    for(auto&& i : item){
        cin >> i.first >> i.second;
    }
    memset(dp, -1, sizeof dp);
    cout << dfs(0) << "\n";
}