#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define INF 2000000000 using namespace std; int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1}; int gcd(int a,int b){if(a%b==0){return b;}else return gcd(b,a%b);} int lcm(int a,int b){if(a==0){return b;} return a/gcd(a,b)*b;} int MOD; template void mod(T &n){MOD=n;} #define sym cout<<"---------"< #define P pair #define mk make_pair #define en endl #define WHITE 1 #define BLACK 2 #define GRAY 1 #define RE return 0 #define int ll signed main(){ cout<>n; double d=0; for(int i=1; i<=6; i++){ d+=i*n/6; } cout<