#include <stdio.h>#include <stdlib.h>#define MAX_N 780struct frac { int up, down;};struct point { int x, y;};struct slash_node { int from, to; struct frac k;};struct ans_node { int id[MAX_N], len;};struct seg_node { int start, end;};struct slash_node slash[MAX_N * MAX_N];struct point in[MAX_N];struct ans_node ans[MAX_N];char visited[MAX_N][MAX_N];int N, ans_cnt, slash_cnt;__inline int gcd(int a, int b){ int r; if (a < b) { r = a; a = b; b = r; } while (1) { r = a % b; if (!r) return b; a = b; b = r; }}__inline struct frac frac_init(int up, int down){ int r, s; struct frac f; if (!down) { f.down = 1; f.up = 200000; return f; } if (!up) { f.down = 1; f.up = 0; return f; } if (up < 0) { up = -up; s = -1; } else s = 1; r = gcd(up, down); f.up = up / r; f.up *= s; f.down = down / r; return f;}__inline int frac_cmp(struct frac fa, struct frac fb){ return fa.up * fb.down - fa.down * fb.up;}int cmp_slash(const void *a, const void *b){ struct slash_node *p, *q; int r; p = (struct slash_node *)a; q = (struct slash_node *)b; if (p->from != q->from) return p->from - q->from; r = frac_cmp(p->k, q->k); if (!r) return p->to - q->to; return r;}__inline void add_slash(int from, int to){ struct slash_node *s; if (visited[from][to]) return ; s = &slash[slash_cnt++]; s->from = from; s->to = to; if (in[from].x < in[to].x) s->k = frac_init(in[to].y - in[from].y, in[to].x - in[from].x); else s->k = frac_init(in[from].y - in[to].y, in[from].x - in[to].x);}__inline void update(int start, int end){ int i; struct ans_node *a; a = &ans[ans_cnt++]; a->len = 0; a->id[a->len++] = slash[start].from; for (i = start; i <= end; i++) a->id[a->len++] = slash[i].to; for ( ; start <= end - 1; start++) for (i = start + 1; i <= end; i++) visited[slash[start].to][slash[i].to] = 1;}__inline int cmp_seg(struct seg_node *a, struct seg_node *b){ return slash[a->start].to - slash[b->start].to;}__inline void swap_seg(struct seg_node *a, struct seg_node *b){ struct seg_node t = *a; *a = *b; *b = t;}__inline void bsort(struct seg_node *arr, int len){ int i, j; for (i = 0; i < len - 1; i++) for (j = i; j < len - 1; j++) if (cmp_seg(&arr[j], &arr[j + 1]) > 0) swap_seg(&arr[j], &arr[j + 1]); }__inline int calc(int i){ int from, start, cnt, j; static struct seg_node arr[MAX_N]; cnt = 0; for (from = slash[i].from; slash[i].from == from; i++) { start = i; while (i + 1 < slash_cnt && slash[i + 1].from == from && !frac_cmp(slash[i + 1].k, slash[i].k) ) i++; if (i - start >= 1) { arr[cnt].start = start; arr[cnt].end = i; cnt++; } } if (cnt) { bsort(arr, cnt); for (j = 0; j < cnt; j++) update(arr[j].start, arr[j].end); } return i;}__inline void dump_ans(struct ans_node *a){ int i, j, k; for (i = 0; i < a->len - 2; i++) for (j = i + 1; j < a->len - 1; j++) for (k = j + 1; k < a->len; k++) printf("%d %d %dn", a->id[i], a->id[j], a->id[k]);}int main(){ int i, j, cnt; scanf("%d", &N); for (i = 1; i <= N; i++) scanf("%d%d", &in[i].x, &in[i].y); slash_cnt = 0; for (i = 1; i <= N; i++) for (j = i + 1; j <= N; j++) add_slash(i, j); qsort(slash, slash_cnt, sizeof(slash[0]), cmp_slash); for (i = 0; i < slash_cnt; i++) i = calc(i); cnt = 0; for (i = 0; i < ans_cnt; i++) cnt += (ans[i].len) * (ans[i].len - 1) * (ans[i].len - 2) / 6; printf("%dn", cnt); for (i = 0; i < ans_cnt; i++) dump_ans(&ans[i]); return 0;}
