#include<bits/stdc++.h>
#define cir(x) memset(x,0,sizeof(x))
#define LL long long
using namespace std;
const int N=1e3+10;
int a[N],b[N];
int c[N],d[N];
int n,m,T;
int main(){
    scanf("%d",&T);
    while(T--){
        scanf("%d",&n);
        for(int i=1;i<=n;i++)
            scanf("%d%d",a+i,b+i);
        int ct = 0,l = a[1],r = b[1];
        for(int i=2;i<=n;i++){
            if(r<a[i] || l>b[i]){
                c[++ct] = l;
                d[ct] = r;
                l = a[i];
                r = b[i];
            }else{
                l=max(l,a[i]);
                r=min(r,b[i]);
            }
        }
        c[++ct] = l;
        d[ct] = r;
        int pos = c[1];
        if(ct == 1){
            printf("0\n");
            continue;
        }
        if(d[1] < c[2]){
            pos = d[1];
        }
        LL ans = 0;
        for(int i=2;i<=ct;i++){
            if(pos > d[i]){
                if((pos - d[i]) %2 == 1 && d[i] - c[i] > 0 && i < ct && d[i+1] < c[i]){
                    ans += (pos - d[i] + 1) / 2;
                    pos = d[i] - 1;
               }
               else{
                    ans += (pos - d[i] + 1) / 2;
                    pos = d[i];
               }
            }else {
                if((c[i] - pos) %2 == 1 && d[i] - c[i] > 0 && i < ct && c[i+1] > d[i]){
                    ans += (c[i] - pos + 1) / 2;
                    pos = c[i] + 1;
               }
               else{
                    ans += (c[i] - pos + 1) / 2;
                    pos = c[i];
               }
            }
        }
        printf("%I64d\n",ans);
    }
    return 0;
}