#pragma region Macros
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define rep2(i, a, b) for(ll i = a; i <= b; ++i)
#define rep(i, n) for(ll i = 0; i < n; ++i)
#define rep3(i, a, b) for(ll i = a; i >= b; --i)
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define eb emplace_back
#define vi vector<int>
#define vec vector<int>
#define vll vector<ll>
#define vpi vector<pii>
#define vpll vector<pll>
#define overload2(_1, _2, name, ...) name
#define vv(a, b) vector<vector<int>>(a, vector<int>(b))
#define vv2(a, b, c) vector<vector<int>>(a, vector<int>(b, c))
#define vvl(a, b) vector<vector<ll>>(a, vector<ll>(b))
#define vvl2(a, b, c) vector<vector<ll>>(a, vector<ll>(b, c))
#define vvv(a, b, c) vector<vv(b, c)>(a)
#define vvv2(a, b, c, d) vector<vv(b, c, d)>(a)
#define vvvl(a, b, c) vector<vvl(b, c)>(a)
#define vvvl2(a, b, c, d) vector<vvl(b, c, d)>(a)
#define fi first
#define se second
#define all(c) begin(c), end(c)
#define ios ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define lb(c, x) distance((c).begin(), lower_bound(all(c), (x)))
#define ub(c, x) distance((c).begin(), upper_bound(all(c), (x)))
using namespace std;
template <class T>
using pq = priority_queue<T>;
template <class T>
using pqg = priority_queue<T, vector<T>, greater<T>>;
#define Size(c) (int)(c).size()
#define INT(...)     \
    int __VA_ARGS__; \
    IN(__VA_ARGS__)
#define LL(...)     \
    ll __VA_ARGS__; \
    IN(__VA_ARGS__)
#define ULL(...)     \
    ull __VA_ARGS__; \
    IN(__VA_ARGS__)
#define STR(...)        \
    string __VA_ARGS__; \
    IN(__VA_ARGS__)
#define CHR(...)      \
    char __VA_ARGS__; \
    IN(__VA_ARGS__)
#define DBL(...)        \
    double __VA_ARGS__; \
    IN(__VA_ARGS__)
#define LD(...)     \
    ld __VA_ARGS__; \
    IN(__VA_ARGS__)
#define VEC(type, name, size) \
    vector<type> name(size);  \
    IN(name)
#define VV(type, name, h, w)                       \
    vector<vector<type>> name(h, vector<type>(w)); \
    IN(name)
int scan() { return getchar(); }
void scan(int& a) { cin >> a; }
void scan(long long& a) { cin >> a; }
void scan(char& a) { cin >> a; }
void scan(double& a) { cin >> a; }
void scan(long double& a) { cin >> a; }
void scan(char a[]) { scanf("%s", a); }
void scan(string& a) { cin >> a; }
template <class T>
void scan(vector<T>&);
template <class T, size_t size>
void scan(array<T, size>&);
template <class T, class L>
void scan(pair<T, L>&);
template <class T, size_t size>
void scan(T (&)[size]);
template <class T>
void scan(vector<T>& a) {
    for(auto& i : a) scan(i);
}
template <class T>
void scan(deque<T>& a) {
    for(auto& i : a) scan(i);
}
template <class T, size_t size>
void scan(array<T, size>& a) {
    for(auto& i : a) scan(i);
}
template <class T, class L>
void scan(pair<T, L>& p) {
    scan(p.first);
    scan(p.second);
}
template <class T, size_t size>
void scan(T (&a)[size]) {
    for(auto& i : a) scan(i);
}
template <class T>
void scan(T& a) {
    cin >> a;
}
void IN() {}
template <class Head, class... Tail>
void IN(Head& head, Tail&... tail) {
    scan(head);
    IN(tail...);
}
string stin() {
    string s;
    cin >> s;
    return s;
}
template <class T>
inline bool chmax(T& a, T b) {
    if(a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
    if(a > b) {
        a = b;
        return 1;
    }
    return 0;
}
vi iota(int n) {
    vi a(n);
    iota(all(a), 0);
    return a;
}
template <class T>
void UNIQUE(vector<T>& x) {
    sort(all(x));
    x.erase(unique(all(x)), x.end());
}
int in() {
    int x;
    cin >> x;
    return x;
}
ll lin() {
    unsigned long long x;
    cin >> x;
    return x;
}
void print() { putchar(' '); }
void print(bool a) { cout << a; }
void print(int a) { cout << a; }
void print(long long a) { cout << a; }
void print(char a) { cout << a; }
void print(string& a) { cout << a; }
void print(double a) { cout << a; }
template <class T>
void print(const vector<T>&);
template <class T, size_t size>
void print(const array<T, size>&);
template <class T, class L>
void print(const pair<T, L>& p);
template <class T, size_t size>
void print(const T (&)[size]);
template <class T>
void print(const vector<T>& a) {
    if(a.empty()) return;
    print(a[0]);
    for(auto i = a.begin(); ++i != a.end();) {
        cout << " ";
        print(*i);
    }
    cout << endl;
}
template <class T>
void print(const deque<T>& a) {
    if(a.empty()) return;
    print(a[0]);
    for(auto i = a.begin(); ++i != a.end();) {
        cout << " ";
        print(*i);
    }
}
template <class T, size_t size>
void print(const array<T, size>& a) {
    print(a[0]);
    for(auto i = a.begin(); ++i != a.end();) {
        cout << " ";
        print(*i);
    }
}
template <class T, class L>
void print(const pair<T, L>& p) {
    cout << '(';
    print(p.first);
    cout << ",";
    print(p.second);
    cout << ')';
}
template <class T>
void print(set<T>& x) {
    for(auto e : x) print(e), cout << " ";
    cout << endl;
}
template <class T>
void print(multiset<T>& x) {
    for(auto e : x) print(e), cout << " ";
    cout << endl;
}
template <class T, size_t size>
void print(const T (&a)[size]) {
    print(a[0]);
    for(auto i = a; ++i != end(a);) {
        cout << " ";
        print(*i);
    }
}
template <class T>
void print(const T& a) {
    cout << a;
}
int out() {
    putchar('\n');
    return 0;
}
template <class T>
int out(const T& t) {
    print(t);
    putchar('\n');
    return 0;
}
template <class Head, class... Tail>
int out(const Head& head, const Tail&... tail) {
    print(head);
    putchar(' ');
    out(tail...);
    return 0;
}
ll gcd(ll a, ll b) {
    while(b) {
        ll c = b;
        b = a % b;
        a = c;
    }
    return a;
}
ll lcm(ll a, ll b) {
    if(!a || !b) return 0;
    return a * b / gcd(a, b);
}
vector<pll> factor(ll x) {
    vector<pll> ans;
    for(ll i = 2; i * i <= x; i++)
        if(x % i == 0) {
            ans.push_back({i, 1});
            while((x /= i) % i == 0) ans.back().second++;
        }
    if(x != 1) ans.push_back({x, 1});
    return ans;
}
vector<int> divisor(int x) {
    vector<int> ans;
    for(int i = 1; i * i <= x; i++)
        if(x % i == 0) {
            ans.pb(i);
            if(i * i != x) ans.pb(x / i);
        }
    return ans;
}
int popcount(ll x) { return __builtin_popcountll(x); }
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int rnd(int n) { return uniform_int_distribution<int>(0, n - 1)(rng); }
#define endl '\n'

#ifdef _LOCAL
#undef endl
#define debug(x)        \
    cout << #x << ": "; \
    print(x);           \
    cout << endl;
void err() {}
template <class T>
void err(const T& t) {
    print(t);
    cout << " ";
}
template <class Head, class... Tail>
void err(const Head& head, const Tail&... tail) {
    print(head);
    putchar(' ');
    out(tail...);
}
#else
#define debug(x)
template <class... T>
void err(const T&...) {}
#endif

struct Setup_io {
    Setup_io() {
        ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
        cout << fixed << setprecision(15);
    }
} setup_io;
#pragma endregion

// _______ここから編集！_______________

main() {
    DBL(p);
    cout << (1.0 / (1.0 - p)) - 1 << endl;
}