#include<stdio.h>
int main()
{
long s=0,dr,st,n,i,st1,dr1,aux;
freopen("heavymetal.in","r",stdin);
freopen("heavymetal.out","w",stdout);

//freopen("heavymet.in","r",stdin);
//freopen("heavymet.out","w",stdout);

scanf("%ld",&n);
scanf("%ld%ld",&st,&dr);
s=dr-st;
if(st>dr)
{
aux=st;
st=dr;
dr=aux;
}
for(i=2;i<=n;i++)
{
scanf("%ld%ld",&st1,&dr1);
if(st1>dr1)
{
aux=st1;
st1=dr1;
dr1=aux;
}
if(st1-st==0 || st1-st==1)
{
dr=dr1;
s=s+(dr1-st1);
}
else
if(st-dr1==0 || st-dr1==1)
{
st=dr1;
s=s+(dr1-st1);
}
else
if(st1>=st && dr1<=dr)
s+=0;
else
if(st1>=dr)
{
st=st1;
dr=dr1;
s=s+(dr1-st1);
}
}
printf("%ld",s);
fcloseall();
return 0;
}