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Cod sursa(job #51036)
// N^3 * log N
#include <stdio.h>
#include <fstream>
#include <algorithm>
using namespace std;
#define in "oite.in"
#define out "oite.out"
#define dim 1025
int C[dim];
bool sel[1000001];
int N, L, S;
int t = 0;
bool Search(int st, int dr, int val);
int main()
{
freopen(in,"r",stdin);
freopen(out,"w",stdout);
scanf("%d%d", &N, &L);
for ( int i = 1; i <= N; i++ )
scanf("%d", &C[i]), sel[C[i]] = 1;
sort(C,C+N+1);
t = 0;
for ( int i = 1; i < N-1; i++ )
for ( int j = i+1; j < N; j++ )
for ( int k = j+1; k <= N; k++ )
{
S = L - C[i] - C[j] - C[k];
if ( S < 0 || S < C[k] || S == C[k] && C[k+1] != S ) continue;
else
{
if ( sel[S] == 1 )
{
// printf("%d %d %d\n", i, j, k);
t += 1;
}
}
}
printf("%d", t);
}
bool Search(int st, int dr, int val)
{
int mij = 0;
bool ok = 0;
while ( st <= dr )
{
int mij = (st+dr)>>1;
if ( C[mij] == val ) ok = 1, st = dr + 1;
else if ( C[mij] > val ) dr = mij - 1;
else if ( C[mij] < val ) st = mij + 1;
}
return ok;
}