#include<iostream>
#include<vector>
using namespace std;

double pi = 3.1415927;
double area(double r) { return pi*r*r; }

void f() {
  double savedpi = pi;
  pi = 0;
  cout << area(51) << endl;
  pi = savedpi
}

int main() {
  
  /*
  vector<int> v{1,2,3};
  for(auto x:v) v.push_back(x);
  for(auto x:v) cout << x << endl;
  *
}