#include using namespace std; struct iofast_t { iofast_t() { ios::sync_with_stdio(false); cin.tie(nullptr); } } iofast; struct uns_t {} uns; template auto vec(Element init, Head arg, Args ...args) { if constexpr (sizeof...(Args) == 0) return vector(arg, init); else return vector(arg, vec(init, args...)); } template auto vec(uns_t, Head arg, Args ...args) { return vec(Element(), arg, args...); } template auto distance(const Container &c, decltype(begin(c)) iter) { return distance(begin(c), iter); } template ::value_type>> auto isort(RIter first, RIter last, Compare comp = Compare()) { vector i(distance(first, last)); iota(begin(i), end(i), 0); sort(begin(i), end(i), [&](auto x, auto y) { return comp(*(first + x), *(first + y)); }); return i; } template typename, typename = void_t<>> struct detect : false_type {}; template typename Check> struct detect>> : true_type {}; template typename Check> constexpr inline bool detect_v = detect::value; template using has_member_sort = decltype(declval().sort()); template > auto sorted(Container c, Compare comp = Compare()) { if constexpr (detect_v) { c.sort(comp); return c; } else { sort(begin(c), end(c), comp); return c; } } template > auto uniqued(Container c, Compare comp = Compare()) { c.erase(unique(begin(c), end(c), comp), end(c)); return c; } template > T &chmin(T &l, T r, Compare &&f = less()) { return l = min(l, r, f); } template > T &chmax(T &l, T r, Compare &&f = less()) { return l = max(l, r, f); } template constexpr auto fix(F &&f) noexcept { return [f = std::tuple(std::forward(f))](auto &&...args) mutable { return std::get<0>(f)(fix(std::get<0>(f)), std::forward(args)...); }; } /* int64_t sign(int64_t x) { return clamp(x, -1, 1); } int64_t floor(int64_t x, int64_t y) { if (0 < sign(x) * sign(y)) { return x / y; } return -((abs(x) + abs(y) - 1) / abs(y)); } int64_t ceil(int64_t x, int64_t y) { if (0 < sign(x) * sign(y)) { return (abs(x) + abs(y) - 1) / abs(y); } return x / y; } auto exgcd(int a, int b) -> tuple { if (b != 0) { auto [xp, yp] = exgcd(b, a % b); return { yp, xp - (a / b) * yp }; } if (0 <= a) { return { 1, 0 }; } return { -1, 0 }; } int f(int x, int y) { if (x == 0 || y == 0 || gcd(x, y) != 1) { return 0; } auto [xp, yp] = exgcd(x, y); auto check = [&](int c) { return 0 <= floor(yp * c, x) - ceil(-xp * c, y); }; int k = x * y; while (0 < k && check(k - 1)) { --k; } return k; } int main() { for (int i = 1; i <= 100; ++i) { for (int j = 1; j <= 100; ++j) { if (gcd(i, j) == 1) { if ((i - 1) * (j - 1) != f(i, j)) { cout << "ng" << endl; } } } } } */ int64_t f(int64_t x, int64_t y) { if (x == 0 || y == 0 || gcd(x, y) != 1) { return 0; } return (x - 1) * (y - 1); } int main() { int n; cin >> n; auto a = vec(uns, n); for (auto &e : a) cin >> e; if (count(begin(a), end(a), 0) != 0) { int iter1 = 0; while (a[iter1] != 0) { ++iter1; } int iter2 = n - 1; while (iter1 == iter2) { --iter2; } cout << 0 << endl; cout << iter1 + 1 << " " << iter2 + 1 << endl; for (int i = 1; i < n - 1; ++i) { cout << (n - i) << " " << (n - i - 1) << endl; } return 0; } int even = 0; for (auto v : a) { even += (v % 2 == 0); } if (2 <= even) { int iter1 = 0; while (a[iter1] % 2 != 0) { ++iter1; } int iter2 = n - 1; while (a[iter2] % 2 != 0) { --iter2; } cout << 0 << endl; cout << iter1 + 1 << " " << iter2 + 1 << endl; for (int i = 1; i < n - 1; ++i) { cout << (n - i) << " " << (n - i - 1) << endl; } return 0; } if (n == 2) { cout << f(a[0], a[1]) << endl; cout << 1 << " " << 2 << endl; return 0; } if (1 <= even) { int iter1 = 0; while (a[iter1] % 2 != 0) { ++iter1; } int iter2 = 0; while (iter1 == iter2) { ++iter2; } cout << 0 << endl; cout << iter1 + 1 << " " << iter2 + 1 << endl; for (int i = 1; i < n - 1; ++i) { cout << (n - i) << " " << (n - i - 1) << endl; } return 0; } int odd = 0; for (auto v : a) { odd += (v % 2 == 1); } if (n == 3 && odd == 3) { cout << a[0] * a[1] * a[2] << endl; cout << 1 << " " << 2 << endl; for (int i = 1; i < n - 1; ++i) { cout << (n - i) << " " << (n - i - 1) << endl; } return 0; } cout << 0 << endl; cout << 1 << " " << 2 << endl; for (int i = 1; i < n - 1; ++i) { cout << (n - i) << " " << (n - i - 1) << endl; } }