#include <iostream>
#include <algorithm>
using namespace std;
const int MAXN=3005;
typedef long long int ll;
const ll INF=0x3f3f3f3f3f3f3f3f;
ll dp[MAXN][2],idx; // dp[i][0] i为红色时需要的最小代价
struct line{
    int st,en;
    inline void read(){
        cin>>this->st>>this->en;
    }
    inline bool operator<(const line &other)const{
        return this->en<other.en;
    }
}ls[MAXN];
int n,mst;
int main(int argc, char const *argv[])
{
    ios::sync_with_stdio(false);
    cin>>n;
    for(int i=1;i<=n;i++)
        ls[i].read();
    sort(ls+1,ls+1+n);
    ls[0].st=ls[0].en=-2e9;
    for(int i=1;i<=n;i++){
        mst=ls[i].st;
        idx=i-1;
        dp[i][1]=INF;
        if(idx)
            while(mst<=ls[idx].en){
                dp[i][1]=min(dp[i][1],dp[idx][0]);
                mst=max(mst,ls[idx].st);
                idx--;
                if(!idx)
                    break;
            }
        dp[i][0]=ls[i].en-ls[i].st+min(dp[idx][0],dp[idx][1]);
    }
    // for(int i=1;i<=n;i++)
        // cout<<ls[i].st<<"->"<<ls[i].en<<':'<<dp[i][0]<<','<<dp[i][1]<<endl;
    cout<<min(dp[n][0],dp[n][1])<<endl;
    return 0;
}