#include<bits/stdc++.h>
#define rep(x,y,z) for(int x=y;x<=z;x++)
#define drep(x,y,z) for(int x=y;x>=z;x--)
#define ull unsigned long long
#define ll long long
using namespace std;
inline int read()
{
	int x=0;bool flag=1;char ch=getchar();
	while(ch<'0'||ch>'9') {if(ch=='-')flag=0;ch=getchar();}
	while(ch>='0'&&ch<='9') {x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}
	if(flag) return x;
	return ~(x-1);
} 
inline void write(int x)
{
	if(x<0) {x=~(x-1);putchar('-');}
	if(x>9) write(x/10);
	putchar(x%10+'0');
}
///////////////////////////////////////
const int N=1e2+5;
const int L=1e4+50;
int nc,lc;
int a[N];
ll ans;
inline int IF(int x,int y)
{
	rep(i,1,x-1)
	{
		if(a[x]-a[x-i]!=a[y+i]-a[y]) return 0;
	}
	return 1;
}
int vv;
void solve()
{
	rep(i,1,nc>>1)
	{
		if((a[i+1]+a[i])&1) continue;
		ans+=IF(i,i+1);
		if(a[i+1]<<1==a[i]+a[i+2]) ans+=IF(i,i+2);
	}
	return;
}
int main()
{
    freopen("device.in","r",stdin);
	freopen("device.out","w",stdout);
	nc=read(),lc=read();
	rep(i,1,nc) a[i]=read();
	sort(a+1,a+nc+1);
	solve();
	rep(i,1,nc) a[i]=lc-a[i];
	vv=lc;
	sort(a+1,a+nc+1);
	solve();
	cout<<ans<<endl;
    return 0;
}