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#include <bits/stdc++.h>
using namespace std;
using ll = long long;

#ifdef DEBUG
#include "debug.h"
#else
#define debug(...) ;
#endif

#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repp(i, n, m) for (int i = (n); i < (m); ++i)

#define repr(i, n) for (int i = (n) - 1; i >= 0; --i)
#define reppr(i, n, m) for (int i = (m) - 1; i >= (n); --i)

using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using pi = pair<int, int>;
using pll = pair<ll, ll>;

template <typename T, typename V> void mini(T& a, V b) {if (b < a) a = b; }
template <typename T, typename V> void maxi(T& a, V b) {if (b > a) a = b; }

void solve() {
    int n, m;
    cin >> n >> m;

    string s;
    cin >> s;

    // assert(n == 1);

    int a = 0, b = 16;

    auto has = [&](int i){
        if (i < 0 || i >= m || s[i] == '.')
            return 0.0;
        if (s[i] == 'O')
            return 1.0;
        else
            return 0.5;
    };

    auto hasnot = [&](int i){
        return 1.0 - has(i);
    };

    rep(i, m) {
        double p1 = hasnot(i-1) * has(i) - hasnot(i-1) * has(i) * has(i+1) * hasnot(i+2);

        debug(i, p1);

        a += p1 * b;
    }

    int g = __gcd(a, b);
    a /= g;
    b /= g;

    cout << a << '/' << b << '\n';
}

int main() {
#ifndef DEBUG
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#endif
    int z = 1;
    // scanf("%d", &z);
    while (z--)
        solve();
    return 0;
}