#include <cstdio>

#include <cstring>

#include <queue>

#include <cmath>

#include <algorithm>

#include <set>

#include <iostream>

#include <map>

#include <stack>

#include <string>

#include <vector>

#define  pi acos(-1.0)

#define  eps 1e-9

#define  fi first

#define  se second

#define  rtl   rt<<1

#define  rtr   rt<<1|1

#define  bug         printf("******\n")

#define  mem(a,b)    memset(a,b,sizeof(a))

#define  name2str(x) #x

#define  fuck(x)     cout<<#x" = "<<x<<endl

#define  f(a)        a*a

#define  sf(n)       scanf("%d", &n)

#define  sff(a,b)    scanf("%d %d", &a, &b)

#define  sfff(a,b,c) scanf("%d %d %d", &a, &b, &c)

#define  sffff(a,b,c,d) scanf("%d %d %d %d", &a, &b, &c, &d)

#define  pf          printf

#define  FRE(i,a,b)  for(i = a; i <= b; i++)

#define  FREE(i,a,b) for(i = a; i >= b; i--)

#define  FRL(i,a,b)  for(i = a; i < b; i++)+

#define  FRLL(i,a,b) for(i = a; i > b; i--)

#define  FIN         freopen("data.txt","r",stdin)

#define  gcd(a,b)    __gcd(a,b)

#define  lowbit(x)   x&-x

#define rep(i,a,b) for(int i=a;i<b;++i)

#define per(i,a,b) for(int i=a-1;i>=b;--i)

using namespace std;

typedef long long  LL;

typedef unsigned long long ULL;

const int maxn = 3e5 + ;

const int maxm = maxn * ;

int n, m, a[maxn], b[maxn];

int len, res[maxm], mx; //开大4倍

struct cpx {

    long double r, i;

    cpx ( long double r = , long double i =  ) : r ( r ), i ( i ) {};

    cpx operator+ ( const cpx &b ) {

        return cpx ( r + b.r, i + b.i );

    }

    cpx operator- ( const cpx &b ) {

        return cpx ( r - b.r, i - b.i );

    }

    cpx operator* ( const cpx &b ) {

        return cpx ( r * b.r - i * b.i, i * b.r + r * b.i );

    }

} va[maxm], vb[maxm];

void rader ( cpx F[], int len ) { //len = 2^M,reverse F[i] with  F[j] j为i二进制反转

    int j = len >> ;

    for ( int i = ; i < len - ; ++i ) {

        if ( i < j ) swap ( F[i], F[j] ); // reverse

        int k = len >> ;

        while ( j >= k ) j -= k, k >>= ;

        if ( j < k ) j += k;

    }

}

void FFT ( cpx F[], int len, int t ) {

    rader ( F, len );

    for ( int h = ; h <= len; h <<=  ) {

        cpx wn ( cos ( -t *  * pi / h ), sin ( -t *  * pi / h ) );

        for ( int j = ; j < len; j += h ) {

            cpx E ( ,  ); //旋转因子

            for ( int k = j; k < j + h / ; ++k ) {

                cpx u = F[k];

                cpx v = E * F[k + h / ];

                F[k] = u + v;

                F[k + h / ] = u - v;

                E = E * wn;

            }

        }

    }

    if ( t == - ) //IDFT

        for ( int i = ; i < len; ++i ) F[i].r /= len;

}

void Conv ( cpx a[], cpx b[], int len ) { //求卷积

    FFT ( a, len,  );

    FFT ( b, len,  );

    for ( int i = ; i < len; ++i ) a[i] = a[i] * b[i];

    FFT ( a, len, - );

}

void gao () {

    len = ;

    mx = n + m;

    while ( len <= mx ) len <<= ; //mx为卷积后最大下标

    for ( int i = ; i < len; i++ ) va[i].r = va[i].i = vb[i].r = vb[i].i = ;

    for ( int i = ; i < n; i++ ) va[i].r = a[i]; //根据题目要求改写

    for ( int i = ; i < m; i++ ) vb[i].r = b[i]; //根据题目要求改写

    Conv ( va, vb, len );

    for ( int i = ; i < len; ++i ) res[i] += ( LL ) floor ( va[i].r + 0.5 );

}

int L[maxn], R[maxn], p[maxn];

int main() {

    //FIN;

    int num;

    sf ( num );

    m = -;

    for ( int i = ; i < num ; i++ ) {

        sf ( p[i] );

        R[p[i]]++;

        m = max ( m, p[i] );

    }

    m++;

    n = m;

    int sz = min ( num,  * ( int ) sqrt ( num ) );

    LL ans = ;

    for ( int i =  ; i < num ; i += sz ) {

        int r = min ( num, i + sz ) - ;

        for ( int j = i ; j <= r ; j++ ) R[p[j]]--;

        for ( int j = i, x ; j <= r ; j++ ) {

            for ( int k = j +  ; k <= r ; k++ ) {

                x =  * p[j] - p[k];

                if ( x >=  ) ans += 1LL * L[x];

                x =  * p[k] - p[j];

                if ( x >=  ) ans += 1LL * R[x];

            }

            L[p[j]]++;

        }

    }

    for ( int i =  ; i < num ; i += sz ) {

        int r = min ( num, i + sz ) - ;

        mem ( a,  ), mem ( b,  ), mem ( res,  );

        for ( int j =  ; j < i ; j++ ) a[p[j]]++;

        for ( int j = r +  ; j < num ; j++ ) b[p[j]]++;

        gao();

        for ( int j = i ; j <= r ; j++ ) ans += 1LL * ( res[ * p[j]] );

    }

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

    return ;

}