# Light OJ 1433 – Minimum Arc Distance

```
#include &lt;bits/stdc++.h&gt;

#define pii pair &lt;int,int&gt;
#define sc scanf
#define pf printf
#define Pi 2*acos(0.0)
#define ms(a,b) memset(a, b, sizeof(a))
#define pb(a) push_back(a)
#define MP make_pair
#define oo 1&lt;&lt;29
#define dd double
#define ll long long
#define EPS 10E-10
#define ff first
#define ss second
#define MAX 10000
#define CIN ios_base::sync_with_stdio(0)
#define SZ(a) (int)a.size()
#define getint(a) scanf(&quot;%d&quot;,&amp;a)
#define getint2(a,b) scanf(&quot;%d%d&quot;,&amp;a,&amp;b)
#define getint3(a,b,c) scanf(&quot;%d%d%d&quot;,&amp;a,&amp;b,&amp;c)
#define loop(i,n) for(int i=0;i&lt;n;i++)
#define TEST_CASE(t) for(int z=1;z&lt;=t;z++)
#define PRINT_CASE printf(&quot;Case %d: &quot;,z)
#define all(a) a.begin(),a.end()
#define intlim 2147483648
#define inf 1000000
#define rtintlim 46340
#define llim 9223372036854775808
#define rtllim 3037000499
#define ull unsigned long long
#define I int

using namespace std;

/* Bits operation */
int Set(int n,int pos)  { return n = n | 1&lt;&lt;pos;}
bool check(int n,int pos) { return n &amp; 1&lt;&lt;pos;}
int Reset(int n, int pos) { return n=n &amp; ~(1&lt;&lt;pos);}

int main()
{
///freopen(&quot;in.txt&quot;,&quot;r&quot;,stdin);
///freopen(&quot;out.txt&quot;,&quot;w&quot;,stdout);
int t,x,y;
getint(t);

TEST_CASE(t)
{
getint2(x,y);
pii o(x,y);
getint2(x,y);
pii a(x,y);
getint2(x,y);
pii b(x,y);
double ab=sqrt((a.ff-b.ff)*(a.ff-b.ff)+(a.ss-b.ss)*(a.ss-b.ss));
double oa=sqrt((a.ff-o.ff)*(a.ff-o.ff)+(a.ss-o.ss)*(a.ss-o.ss));
double ob=sqrt((b.ff-o.ff)*(b.ff-o.ff)+(b.ss-o.ss)*(b.ss-o.ss));
double angle=acos(((oa*oa)+(ob*ob)-(ab*ab))/(2*oa*ob));
PRINT_CASE;
pf(&quot;%lf\n&quot;,angle*ob);
}
return 0;
}

```