Part 2 ques 1

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
#define pi acos(-1)
double areaofcircle(double r)
{
    double area;
    area = pi*r*r;
    return area;
}

int main()
{
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif

    double radius;
    cin >> radius;
    printf("Area of circle = %.2lf\n",areaofcircle(radius));

    return 0;
}