#include <bits/stdc++.h>
using namespace std;

#define int long long
#define debug(x) cout<<#x<<" "<<x<<endl;

const int N=1e6+5;
const double eps=1e-9;
const int INF=1e18;

int T,n;
int a[N],b[N];
int sum;

void solve()
{
    scanf("%I64d",&n);sum=0;
    for(int i=1;i<=n;i++) scanf("%I64d%I64d",&a[i],&b[i]);
    int lpt=a[1],rpt=b[1];
    for(int i=2;i<=n;lpt<a[i]?lpt=a[i]:0,rpt>b[i]?rpt=b[i]:0,i++){
        //debug(lpt),debug(rpt);
        if(rpt>=a[i]&&lpt<=b[i]) continue;
        if(a[i]>rpt){
            sum+=a[i]-rpt>>1;
            if((a[i]-rpt)&1) sum++,lpt=a[i],rpt=a[i]+1;
            //debug(lpt),debug(rpt);
            else lpt=a[i],rpt=a[i];
        }
        else{
            sum+=lpt-b[i]>>1;
            //debug(lpt),debug(rpt);
            if((lpt-b[i])&1) sum++,lpt=b[i]-1,rpt=b[i];
            else lpt=b[i],rpt=b[i];
        }
        //debug(lpt),debug(rpt);
    }
    cout<<sum<<endl;
}

signed main()
{
    //freopen("a.in","r",stdin);
    //freopen("a.out","w",stdout);
    scanf("%I64d",&T);
    while(T--) solve();
    return 0;
}