#include using namespace std; typedef long long ll; typedef unsigned long long ull; typedef double dbl; typedef long double ld; #define FOR(i, a, b) for(int i = (int)(a); i < (int)(b); ++i) #define REP(i, b) FOR(i, 0, b) #define FORLL(i, a, b) for(ll i = (ll)(a); i < (ll)(b); ++i) #define REPLL(i, b) FORLL(i, 0, b) #define ALL(x) (x).begin(),(x).end() const int INF = 1e+9; constexpr int mod(int n) {return n % 1000000007;} template inline Head max(Head head, Tail... tail) {for(Head i: initializer_list{tail...}) if(head < i) head = i; return head;} template inline Head min(Head head, Tail... tail) {for(Head i: initializer_list{tail...}) if(head > i) head = i; return head;} template inline void chmax(T &v, U... a) {v = ::max(v, a...);} template inline void chmin(T &v, U... a) {v = ::min(v, a...);} inline void read(char &v) {v = getchar();} inline void read(int &v) {assert(scanf("%d", &v));} inline void read(ll &v) {assert(scanf("%lld", &v));} inline void read(ull &v) {assert(scanf("%llu", &v));} inline void read(dbl &v) {assert(scanf("%lf", &v));} inline void read(ld &v) {assert(scanf("%Lf", &v));} inline void read(string &v){v.clear(); char buf[512]; do read(*buf); while(*buf == ' ' || *buf == '\n'); for(int pt = 1;;) {read(buf[pt]); if(buf[pt] == ' ' || buf[pt] == '\n') {v.append(buf, pt); break;} if(++pt >= 512) {v.append(buf, 512); pt = 0;}}} template inline void read(vector &v) {int N = v.size(); REP(i, N) read(v[i]);} template inline void read(array &v) {REP(i, N) read(v[i]);} template inline void read(Head &head, Tail &... tail) {read(head); read(tail...);} bool write_space = false; inline void write() {if(write_space) putchar(' '); else write_space = true;} inline void write(char v) {if(v == '\n' || v == ' ') write_space = false; else write(); putchar(v);} inline void write(const char *v){if(!*v) {write(); return;} if(*v != '\n' && *v != ' ') write(); while(*v) putchar(*(v++)); --v; write_space = *v != '\n' && *v != ' ';} inline void write(string &v){write(v.c_str());} inline void write(int v) {write(); printf("%d", v);} inline void write(ll v) {write(); printf("%lld", v);} inline void write(ull v) {write(); printf("%llu", v);} inline void write(dbl v) {write(); printf("%.16f", v);} inline void write(ld v) {write(); printf("%.64Lf", v);} template inline void write(vector &v) {int N = size(v); REP(i, N) write(v[i]); write('\n');} template inline void write(array &v) {REP(i, N) write(v[i]); write('\n');} template inline void write(Head head, Tail... tail) {write(head); write(tail...);} int main() { int n; read(n); write(riemann_zeta(n), '\n'); return 0; }