#include<bits/stdc++.h>

#define pb push_back
#define mp make_pair
#define fi first
#define se second

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

bool chkmax(int &x,int y){return x<y?x=y,true:false;}
bool chkmin(int &x,int y){return x>y?x=y,true:false;}

int readint(){
    int x=0,f=1; char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

int n;
int l[1005],r[1005];

int main(){
    int T=readint();
    while(T--){
        n=readint();
        for(int i=1;i<=n;i++) l[i]=readint(),r[i]=readint();
        if(n==1){
            printf("0\n");
            continue;
        }
        int ans=0,nl=l[1],nr=r[1];
        for(int i=2;i<=n;i++){
            if(max(nl,l[i])<=min(nr,r[i])){
                nl=max(nl,l[i]),nr=min(nr,r[i]);
                continue;
            }
            if(l[i]<nl){
                if((nl-r[i])%2==0) ans+=(nl-r[i])/2,nl=nr=r[i];
                else ans+=(nl-r[i])/2+1,nr=r[i],nl=max(l[i],r[i]-1);
            }
            else{
                if((l[i]-nr)%2==0) ans+=(l[i]-nr)/2,nl=nr=l[i];
                else ans+=(l[i]-nr)/2+1,nl=l[i],nr=min(r[i],l[i]+1);
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}