#include <bits/stdc++.h>
using namespace std;
struct Point {
double x, y;
};
Point a[100005];
int n;
void init() {
cin >> n;
}
void solve() {
for (int i = 0; i < n; i++) {
cin >> a[i].x >> a[i].y;
}
double tong = 0;
for (int i = 0; i < n - 1; i++) {
double dx = a[i + 1].x - a[i].x;
double dy = a[i + 1].y - a[i].y;
tong += sqrt(dx * dx + dy * dy);
}
cout << fixed << setprecision(6) << tong;
}
int main() {
init();
solve();
return 0;
}
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