#include <iostream>
#include <vector>
#include <cinttypes>
#include <unordered_set>

using namespace std;
using int64 = int64_t;

int64 gcd(int64 a, int64 b) {
    while (a != 0 && b != 0) {
        if (a < b) {
            swap(a, b);
        }
        a = a % b;
    }
    return b;
}


int64 inv_cnt(vector<int64> &perm) {
    int64 ans = 0;
    for (int i = 0; i < perm.size(); ++i) {
        for (int j = i + 1; j < perm.size(); ++j) {
            if (perm[i] > perm[j]) {
                ++ans;
            }
        }
    }
    return ans;
}

int64 inv_cnt_ind(vector<int64> &perm, int64 ind) {
    int64 ans = 0;
    for (int i = 0; i < perm.size(); ++i) {
        if ((perm[i] > perm[ind] && i < ind) || (perm[i] < perm[ind] && i > ind)) {
            ++ans;
        }
    }
    return ans;
}

int main() {
    int64 n;
    cin >> n;
    vector<int64> perm(n);
    for (int64 i = 0; i < n; ++i) {
        cin >> perm[i];
    }
    int64 cnt = 0;
    int64 start_cnt = inv_cnt(perm);
    vector<vector<int64>> pr(n, vector<int64>(n, 0));
    for (int i = 0; i < n; ++i) {
        pr[i][i] = inv_cnt_ind(perm, i);
        for (int j = i + 1; j < n; ++j) {
            if (perm[i] < perm[j]) {
                pr[i][j] = pr[i][j - 1] + 1;
            } else {
                pr[i][j] = pr[i][j - 1];
            }
        }
        for (int j = i - 1; j >= 0; --j) {
            if (perm[i] > perm[j]) {
                pr[i][j] = pr[i][j + 1] + 1;
            } else {
                pr[i][j] = pr[i][j + 1];
            }
        }
    }
    for (int i = 0; i < n; ++i) {
        for (int j = i + 1; j < n; ++j) {
            cnt += start_cnt + pr[i][j] + pr[j][i] - pr[i][i] - pr[j][j];
            if (perm[i] > perm[j]) {
                cnt -= 2;
            }
        }
    }

    int64 all = n * (n - 1) / 2;
    int64 g = gcd(cnt, all);
    cout << cnt / g << '/' << all /
                              g;
}