#include <stdio.h>
#define MAXV 7000
int fr[MAXV+1];
int main(){
    int n, i, x, j;
    long long ans;
    FILE *fin, *fout;
    fin=fopen("medie.in", "r");
    fout=fopen("medie.out", "w");
    fscanf(fin, "%d", &n);
    for(i=0; i<n; i++){
        fscanf(fin, "%d", &x);
        fr[x]++;
    }
    ans=0;
    for(i=1; i<=MAXV; i++){
        ans+=(1LL*fr[i]*(fr[i]-1)*(fr[i]-2))/2LL;
        for(j=i+2; j<=MAXV; j+=2){
            ans+=fr[i]*fr[j]*fr[(i+j)/2];
        }
    }
    fprintf(fout, "%lld\n", ans);
    fclose(fin);
    fclose(fout);
    return 0;
}