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

int main(){
    cout.setf(ios_base::fixed);
    cout.precision(3);

    double ar[3][3] = {{0.2,0.5,2.1},
                    {0.15,0.2,2.5},
                    {0.9,5,2.7}};
    cout << "Enter number of data set\n";
    cout << "1, 2 or 3\n";
    int n;cin>>n;
    cout << "Enter x\n";
    double x; cin>>x;
    double a,b,z;
    switch (n)
    {
    case 1:
        a=ar[0][0];b=ar[0][1];z=ar[0][2];
        break;
    case 2:
        a=ar[1][0];b=ar[1][1];z=ar[1][2];
        break;
    case 3:
        a=ar[2][0];b=ar[2][1];z=ar[2][2];
        break;
    }
    if (x < -log(a))
        cout << a*sin(x)*sin(x)+b*cos(z*x);
    else if (-log(a) <= x && x <= b)
        cout << pow(a,b)-pow(cos(a+z*x),3);
    else if (x > b)
        cout << sqrt(2.5*pow(a,3)+pow(b-z*x*x,6));
}