#include<bits/stdc++.h>
#define ll long long
#define N 505
using namespace std;
const ll inf=1e18;
int px[N],py[N],n;
int X[N*2],Y[N*2],m;
ll f[N*2][N*2][2];
int main(){
	ios::sync_with_stdio(0);
	cin>>n;
	for(int i=1;i<=n;++i)cin>>px[i]>>py[i];
	for(int i=1;i<n;++i){
		X[++m]=px[i],Y[m]=py[i];
		if(px[i]<=px[i+1]&&py[i]<=py[i+1])continue;
		if(px[i]>=px[i+1]&&py[i]>=py[i+1])continue;
		X[++m]=min(px[i],px[i+1]),Y[m]=min(py[i],py[i+1]);
	}X[++m]=px[n],Y[m]=py[n];
	n=m+1,X[n]=Y[n]=0;
//	for(int i=0;i<=n;++i)cout<<X[i]<<" "<<Y[i]<<endl;
	for(int i=0;i<=n;++i)
		for(int j=i;j<=n;++j)f[i][j][0]=f[i][j][1]=inf;
	for(int i=n;i>=0;--i)
		for(int j=i;j<=n;++j){
			if(i==j){f[i][j][0]=f[i][j][1]=0;continue;}
			if(j==i+1){
				f[i][j][0]=f[i][j][1]=0;
				ll dx=X[j]-X[i],dy=Y[j]-Y[i];
				if(dx<0)f[i][j][0]-=dx;else f[i][j][1]+=dx;
				if(dy<0)f[i][j][0]-=dy;else f[i][j][1]+=dy;
				continue;
			}
			for(int k=i+1;k<j;++k){
				ll dx=X[k]-X[i],dy=Y[k]-Y[i];
				ll Dx=X[j]-X[k],Dy=Y[j]-Y[k];
				ll a=dx,b=dy,c=Dx,d=Dy;
				if(a<0)a=0;if(b<0)b=0;
				if(c>0)c=0;if(d>0)d=0;
				ll cc=min(a,-c)+min(b,-d)+f[i][k][0]+f[k][j][1];
				if(a+c<0)cc+=-a-c;if(b+d<0)cc+=-b-d;
				f[i][j][0]=min(f[i][j][0],cc);
				cc=min(a,-c)+min(b,-d)+f[i][k][0]+f[k][j][1];
				if(a+c>0)cc+=a+c;if(b+d>0)cc+=b+d;
				f[i][j][1]=min(f[i][j][1],cc);
			}
		}
	cout<<f[0][n][0];
	return 0;
}