#include <cstdio>

 #include <cstring>

 #include <iostream>

 #include <cmath>

 #include <algorithm>

 using namespace std;

 #define INF 0x3f3f3f3f

 #define LL __int64

 int dp[];

 struct node

 {

     int x,y;

 } p[];

 #define eps 1e-6

 int main()

 {

     int t,i,j,n,ans;

     scanf("%d",&t);

     while(t--)

     {

         scanf("%d",&n);

         for(i = ; i < n; i ++)

         {

             scanf("%d%d",&p[i].x,&p[i].y);

         }

         for(i = ; i < ; i ++)

             dp[i] = INF;

         dp[p[].x] = ;

         ans = INF;

         for(i = ; i < n; i ++)

         {

             for(j = p[i].x;; j ++)

             {

                 LL dx = j-p[i].x, dy = p[i].y-p[].y;

                 if( dx*dx+dy*dy > 1LL*p[i].y*p[i].y ) break;

                 if( *p[i].x-j >= p[].x )

                     dp[j] = min(dp[j], dp[*p[i].x-j]+);

                 else

                 break;

                 if( j >= p[n-].x && dp[j] < ans )

                 {

                     ans = dp[j];

                 }

             }

         }

         if(ans >= INF)

             printf("-1\n");

         else

             printf("%d\n",ans);

     }

     return ;

 }