#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#include <bits/stdc++.h>
using namespace std;
#define CRP(t, x) const t &x
#define OPX(op, t, x) operator op(CRP(t, x))
#define OPL(t, x) bool OPX(<, t, x) const
#define FIL(x, v) memset(x, v, sizeof(x))
#define CLR(x) FIL(x, 0)
#define NE1(x) FIL(x, -1)
#define INF(x) FIL(x, 0x3f)
#ifndef _DEBUG
#define _DEBUG 0
#endif // !_DEBUG
#define IFD if (_DEBUG)
typedef int64_t ll, i64;
typedef uint64_t ull, u64;
template <typename T>
using enable_if_arithmetic = typename enable_if<is_arithmetic<T>::value>::type;
template <typename T>
using enable_if_integral = typename enable_if<is_integral<T>::value>::type;
inline char getchar(int)
{
    static char buf[64 << 20], *S = buf, *T = buf;
    if (S == T) T = fread(S = buf, 1, 64 << 20, stdin) + buf;
    return S == T ? EOF : *S++;
}
template <typename T, typename = enable_if_integral<T>>
inline bool read(T &x)
{
    int ch = x = 0, f = 1;
    while (!isdigit(ch = getchar()))
        if (ch == EOF)
            return false;
        else if (ch == '-')
            f = 0;
    for (; isdigit(ch); ch = getchar()) x = x * 10 + ch - '0';
    return x = f ? x : -x, true;
}
template <typename T, typename... Args, typename = enable_if_integral<T>>
inline bool read(T &x, Args &... args) { return read(x) && read(args...); }
ll gcd(ll a, ll b) { return b == 0 ? a : gcd(b, a % b); }
ll fpow(ll a, ll b, ll m)
{
    ll r = 1;
    for (; b; b >>= 1, a = a * a % m)
        if (b & 1) r = r * a % m;
    return r;
}
constexpr double eps = 1e-8;
inline int sgn(double x) { return x > eps ? 1 : x < -eps ? -1 : 0; }
struct P
{
    ll x, y, z;
    bool vis;
    ll dis(CRP(P, rhs)) const { return (x - rhs.x) * (x - rhs.x) + (y - rhs.y) * (y - rhs.y) + (z - rhs.z) * (z - rhs.z); }
} ps[2050];
int main()
{
    int n;
    read(n);
    for (int i = 1; i <= n; i++) read(ps[i].x, ps[i].y, ps[i].z);
    for (;;)
    {
        int fst = 0;
        for (int i = 1; i <= n && !fst; i++)
            if (!ps[i].vis) fst = i;
        if (!fst) break;
        int sec = fst + 1;
        while (ps[sec].vis) sec++;
        for (int i = sec + 1; i <= n; i++)
            if (!ps[i].vis && ps[fst].dis(ps[sec]) > ps[fst].dis(ps[i])) sec = i;
        printf("%d %d\n", fst, sec);
        ps[fst].vis = ps[sec].vis = true;
    }
    return 0;
}