#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int T,n,a[1010],b[1010],p,ans,p1;
int main()
{
    scanf("%d",&T);
    while(T--)
    {
        ans=0;
        scanf("%d",&n);
        for(int i=1;i<=n;++i)scanf("%d %d",&a[i],&b[i]);
        int l=a[1],r=b[1],s;
        for(s=2;s<=n&&((a[s]>=l&&a[s]<=r)||(b[s]>=l&&b[s]<=r)||(a[s]<=l&&b[s]>=r));++s)
            l=max(l,a[s]),r=min(r,b[s]);
        if(a[s]>r)p=p1=r;
        else p=p1=l;
        for(int i=s;i<=n;++i)
        {
            if(p>=a[i]&&p<=b[i])
            {
                if(p1<a[i]||p1>b[i])p1=p;
                continue;
            }
            if(p1>=a[i]&&p1<=b[i])
            {
                p=p1;
                continue;
            }
            if(p<a[i])
            {
                if(p<p1)swap(p,p1);
                ans+=(a[i]-p+1)/2;
                p1=(a[i]-p)&1?a[i]+1:a[i];
                if(p1>b[i])p1=b[i];
                p=a[i];
            }
            else
            {
                if(p>p1)swap(p,p1);
                ans+=(p-b[i]+1)/2;
                p1=(p-b[i])&1?b[i]-1:b[i];
                if(p1<a[i])p1=a[i];
                p=b[i];
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}