127A - Wasted Time - CodeForces Solution

#include <iostream>
using namespace std;
#include<bits/stdc++.h>
int main()
{
int n , k ;
cin >> n ;
cin >> k;
double arr[n][2];
for(int i = 0 ; i < n ; i ++){
    for(int j = 0 ;j < 2; j++){
        cin >> arr[i][j];
    }
}
double arr2[n];
for(int i =0 ;i < n ; i++){
    arr2[i]=sqrt((arr[i][0]-arr[i+1][0])*(arr[i][0]-arr[i+1][0])+(arr[i][1]-arr[i+1][1])*(arr[i][1]-arr[i+1][1]))/50;
}
long double sum =0;
for(int i =0 ;i < n-1 ; i++){
    sum= sum +arr2[i];
}
std::cout << std::setprecision(10) << sum*k << std::endl;
}