Lab task - (Function - 1)

#include <bits/stdc++.h>

#define ll long long
#define ull unsigned long long
#define uom unordered_map
#define pb push_back
#define yes cout<<"YES\n"
#define no cout<<"NO\n"

#define dot(x) fixed<<setprecision(x)
#define wrench786 ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);

#define PI (acos(-1.0))
#define eps 0.00001
const int LIMIT = 10000*1;
const int mod = 1000000007;
using namespace std;

double funck(double radius){
    return (3.1416)*(radius)*(radius);
}

int main(){
    double radius,area;
    cin>>radius;
    area = funck(radius);
    cout<<area<<endl;
}