#include<bits/stdc++.h>
#define il inline
#define vd void
typedef long long ll;
il ll gi(){
    ll x=0,f=1;
    char ch=getchar();
    while(!isdigit(ch))f^=ch=='-',ch=getchar();
    while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
    return f?x:-x;
}
int l[1010],r[1010];
int main(){
#ifdef XZZSB
    freopen("in.in","r",stdin);
    freopen("out.out","w",stdout);
#endif
    int T=gi();
    while(T--){
        int n=gi();
        for(int i=1;i<=n;++i)l[i]=gi(),r[i]=gi();
        int L=l[1],R=r[1];
        for(int i=2;i<=n;++i){
            if(std::max(L,l[i])<=std::min(R,r[i]))L=std::max(l[i],L),R=std::min(r[i],R);
            else{L=R=(L<l[i]?R:L);break;}
        }
        int ans=0;
        for(int i=1;i<=n;++i){
            if(std::max(L,l[i])<=std::min(R,r[i]))L=std::max(l[i],L),R=std::min(r[i],R);
            else if(L<l[i]){// move to R
                ans+=(l[i]-R+1)/2;
                if(l[i]!=r[i]&&(l[i]-R&1))L=l[i],R=l[i]+1;
                else L=R=l[i];
            }else{// move to L
                ans+=(L-r[i]+1)/2;
                if(l[i]!=r[i]&&(L-r[i]&1))L=r[i]-1,R=r[i];
                else L=R=r[i];
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}