#include <stdio.h>
#include <algorithm>
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
class node
{
	private:
	public:
};
namespace root
{
#define lc(id) (id<<1)
#define rc(id) (id<<1|1)
#define lowbit(id) (id&-id)
#define repeat(times) while(times--)
	static const int Buf_size=1<<25,Int_size=25;
	static char F[Int_size];
	static char _c;
	static bool _f;
	static int _x,__cnt;
	static const signed int base_10=10,zero(48),nine(57),flag_signed(45);
	inline int abs(const int &_x)
	{
		return _x<0?-_x:_x;
	}
	inline int max(const int &_x,const int &_y)
	{
		return _x>_y?_x:_y;
	}
	inline int min(const int &_x,const int &_y)
	{
		return _x<_y?_x:_y;
	}
	inline void swap(int &_x,int &_y)
	{
		static int _z;
		_z=_x;
		_x=_y;
		_y=_z;
		return;
	}
	static char buf[Buf_size],*p1=buf,*p2=buf,obuf[Buf_size],*p3=obuf;
#define digit() (zero<=_c&&_c<=nine)
//#define getchar() (p1==p2&&(p2=(p1=buf)+fread(buf,1,Buf_size,stdin),p1==p2)?EOF:*p1++)
#define putchar(x) (p3-obuf<Buf_size)?(*p3++=x):(fwrite(obuf,p3-obuf,1,stdout),p3=obuf,*p3++=x)
	template<typename _Tp,const bool is_signed=false>inline void read(_Tp&_x)
	{
		if(!is_signed)
		{
			_x=0;
			_c=getchar();
			while(!digit())_c=getchar();
			while(digit())
			{
				_x=_x*10+(_c^zero);
				_c=getchar();
			}
			return;
		}
		else
		{
			_x=0;
			_f=false;
			_c=getchar();
			while(!digit())
			{
				if(_c==flag_signed)_f=true;
				_c=getchar();
			}
			while(digit())
			{
				_x=_x*10+(_c^zero);
				_c=getchar();
			}
			if(_f)_x=-_x;
			return;
		}
	}
	inline int read()
	{
		_x=0;
		_c=getchar();
		while(!digit())
		{
			_c=getchar();
		}
		while(digit())
		{
			_x=_x*10+(_c^zero);
			_c=getchar();
		}
		return _x;
	}
	template<typename _Tp>inline void write(_Tp _x)
	{
		if(_x<0)
		{
			putchar(flag_signed);
			_x=-_x;
		}
		if(_x<base_10)
		{
			putchar(_x^zero);
			return;
		}
		write(_x/base_10);
		putchar(_x%base_10^zero);
	}
	inline void out(int x,const char end='\n')
	{
		if(!x)
		{
			putchar(zero);
			putchar(end);
			return;
		}
		if(x<0)
		{
			x=-x;
			putchar(flag_signed);
		}
		__cnt=0;
		while(x)
		{
			F[++__cnt]=x%base_10;
			x/=base_10;
		}
		while(__cnt)
		{
			putchar(F[__cnt]^zero);
			--__cnt;
		}
		putchar(end);
		return;
	}
}
namespace solve
{
	using namespace root;
	inline void debug()
	{
		puts("debug here.");
		return;
	}
	inline void finput(char *stream)
	{
		freopen(stream,"r",stdin);
		return;
	}
	inline void foutput(char *stream)
	{
		freopen(stream,"w",stdout);
		return;
	}
	long long sum;
	class edge
	{
		public:
			long long l,r,length;
			inline void input()
			{
				scanf("%lld %lld",&l,&r);
				length=r-l;
			}
			inline const bool operator<(const edge &other)const
			{
				return l!=other.l?l<other.l:r<other.r;
			}
	}e[30005];
	int i;
	long long f[30005];
	inline void main()
	{
		finput("ex.in");
		int n=read();
		for(i=1;i<=n;++i)
		{
			e[i].input();
		}
		std::sort(e+1,e+n+1);
		for(i=1;i<n;++i)
			f[i]=1ll<<50;
		f[n]=e[n].length;
		for(i=n;i;--i)
		{
			int pos=i+1;
			while(pos<=n&&(e[pos].l<=e[i].r))
				++pos;
			while(pos<=n)
			{
				f[i]=std::min(f[i],f[pos]+e[i].length);
				break;
//				++pos;
			}
//			printf("%lld %lld",f[i],e[i].length);
		}
		long long ans=1ll<<60;
		for(i=1;i<=n;++i)
		{
			if(e[i].l<=e[1].r)
				ans=std::min(ans,f[i]);
		}
		printf("%lld\n",ans);
	}
}
signed main()
{
	solve::main();
	return 0;
}

f[i] 表示 $n\sim i$ 处理完毕，且 $i$ 为红线的最小价值。