include [HTML_REMOVED]

include [HTML_REMOVED]

include [HTML_REMOVED]

using namespace std;

int main()
{
int T;
scanf(“%d”,&T);
while(T–)
{
scanf(“%d%d”,&n,&m);
for (int i = 1; i < =n; i ) scanf(“%d”, &a[i]);
a[ n] = m;
s1[n] = s2[n] = 0;
for (int i = n - 1; i > = 0; i –)
{
s1[i]= s1[i +1], s2[i]= s2[i + 1];
if (i % 2 == 0) s1[i] +=a[i + 1] -a[i];
else s2[i] +=a[i + 1] -a[i];
}
int res =s1[0];
for (int i = 0; i < n; i ++ )
{
int t = a[i + 1]-a[i];
if (t == 1) continue;
res =max(res, s1[0] - s1[i] + s2[i + 1] + t - 1);
}
printf(“%d\n”,res);
}
}