#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
inline void rd(double &x){
  int k;
  int m=0;
  int p=0;
  double r = 1;
  x = 0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m = 1;
      break;
    }
    if(k=='.'){
      p = 1;
      break;
    }
    if('0'<=k&&k<='9'){
      x = k - '0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k=='.'){
      p = 1;
      continue;
    }
    if(k<'0'||k>'9'){
      break;
    }
    if(p){
      r *= 0.1;
      x += r * (k - '0');
    }
    else{
      x = x * 10 + k - '0';
    }
  }
  if(m){
    x = -x;
  }
}
struct MY_WRITER{
  char buf[1048576];
  int s;
  int e;
  MY_WRITER(){
    s = 0;
    e = 1048576;
  }
  ~MY_WRITER(){
    if(s){
      fwrite_unlocked(buf, 1, s, stdout);
    }
  }
}
;
MY_WRITER MY_WRITER_VAR;
void my_putchar_unlocked(int a){
  if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){
    fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout);
    MY_WRITER_VAR.s = 0;
  }
  MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a;
}
inline void wt_L(char a){
  my_putchar_unlocked(a);
}
int WRITER_DOUBLE_DIGIT = 15;
inline int writerDigit_double(){
  return WRITER_DOUBLE_DIGIT;
}
inline void writerDigit_double(int d){
  WRITER_DOUBLE_DIGIT = d;
}
inline void wt_L(double x){
  const int d = WRITER_DOUBLE_DIGIT;
  int k;
  int r;
  double v;
  if(x!=x || (x==x+1 && x==2*x)){
    my_putchar_unlocked('E');
    my_putchar_unlocked('r');
    my_putchar_unlocked('r');
    return;
  }
  if(x < 0){
    my_putchar_unlocked('-');
    x = -x;
  }
  x += 0.5 * pow(0.1, d);
  r = 0;
  v = 1;
  while(x >= 10*v){
    v *= 10;
    r++;
  }
  while(r >= 0){
    r--;
    k = floor(x / v);
    if(k >= 10){
      k = 9;
    }
    if(k <= -1){
      k = 0;
    }
    x -= k * v;
    v *= 0.1;
    my_putchar_unlocked(k + '0');
  }
  if(d > 0){
    my_putchar_unlocked('.');
    v = 1;
    for(r=(0);r<(d);r++){
      v *= 0.1;
      k = floor(x / v);
      if(k >= 10){
        k = 9;
      }
      if(k <= -1){
        k = 0;
      }
      x -= k * v;
      my_putchar_unlocked(k + '0');
    }
  }
}
double X;
double solve(double X){
  int j;
  double res = 0;
  double tmp;
  if(X==0){
    res += 1;
  }
  else{
    res += sin(X) * sin(X) / X / X;
  }
  for(j=(1);j<(1000000);j++){
    tmp = sin(X+j) / (X+j);
    res += tmp * tmp;
  }
  return res;
}
int main(){
  double res = 0;
  double add = 0;
  double tmp;
  rd(X);
  while(X >= 1){
    X--;
    if(X==0){
      tmp = 1;
    }
    else{
      tmp = sin(X) / X;
    }
    add -= tmp * tmp;
  }
  res = 2.07079632677096370230;
  res -= solve(0);
  res += solve(X);
  wt_L(res+add);
  wt_L('\n');
  return 0;
}
// cLay varsion 20200509-1

// --- original code ---
// double X;
// 
// double solve(double X){
//   double res = 0, tmp;
//   if(X==0) res += 1; else res += sin(X) * sin(X) / X / X;
//   rep(j,1,1d6){
//     tmp = sin(X+j) / (X+j);
//     res += tmp * tmp;
//   }
//   return res;
// }
// 
// {
//   double res = 0, add = 0, tmp;
//   rd(X);
// 
//   while(X >= 1){
//     X--;
//     if(X==0) tmp = 1; else tmp = sin(X) / X;
//     add -= tmp * tmp;
//   }
// 
//   res = 2.07079632677096370230;
//   res -= solve(0);
//   res += solve(X);
// 
//   wt(res+add);
// }