#include<bits/stdc++.h>
#define int long long
using namespace std;
inline int read()
{
   int x=0,f=1;char ch=getchar();
   while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
   while (ch>='0'&&ch<='9'){x=(x<<3)+(x<<1)+ch-48;ch=getchar();}
   return x*f;
}
void write(int x)
{
   if(x<0)putchar('-'),x=-x;
   if(x<10)putchar(x+'0');
   else write(x/10),putchar(x%10+'0');
}
const int N=1e5;
const int mod=1e9+7;
int dp[N][2][2];
int n;
int a[N];
int b[N]; 
signed main(){
//	freopen("even.in","r",stdin);
//	freopen("even.out","w",stdout);
	n=read();
	for(int i=1;i<=n;i++)a[i]=read(),b[i]=read();
	memset(dp,0x3f3f,sizeof dp);
//	cout<<dp[0][0][0]<<"??\n"; 
	dp[0][0][0]=dp[0][0][1]=dp[0][1][0]=dp[0][1][1]=0ll; 
	for(int i=1;i<=n;i++){
		dp[i][0][0]=min(dp[i-1][0][0],dp[i-1][1][0])+a[i];
		if(dp[i-1][0][1]<=a[i])dp[i][0][0]=min(dp[i][0][0],a[i]-dp[i-1][0][1]);
		if(dp[i-1][1][1]<=a[i])dp[i][0][0]=min(dp[i][0][0],a[i]-dp[i-1][1][1]);
		if(dp[i-1][0][1]>a[i])dp[i][0][1]=min(dp[i][0][1],dp[i-1][0][1]-a[i]);
		if(dp[i-1][1][1]>a[i])dp[i][0][1]=min(dp[i][0][1],dp[i-1][1][1]-a[i]);	
		dp[i][1][1]=min(dp[i-1][0][1],dp[i-1][1][1])+b[i];
		if(dp[i-1][0][0]<=b[i])dp[i][1][1]=min(dp[i][1][1],b[i]-dp[i-1][0][0]);
		if(dp[i-1][1][0]<=b[i])dp[i][1][1]=min(dp[i][1][1],b[i]-dp[i-1][1][0]);
		if(dp[i-1][0][0]>b[i])dp[i][1][0]=min(dp[i][1][0],dp[i-1][0][0]-b[i]);
		if(dp[i-1][1][0]>b[i])dp[i][1][0]=min(dp[i][1][0],dp[i-1][1][0]-b[i]);
	//	cout<<dp[i][0][0]<<" "<<dp[i][0][1]<<" "<<dp[i][1][0]<<" "<<dp[i][1][1]<<"\n"; 
	} 
	cout<<min(dp[n][0][0],min(dp[n][0][1],min(dp[n][1][0],dp[n][1][1])))<<"\n";
    return 0;
}