#include <stdlib.h>
#include <stdio.h>

#define ll long long

ll *x, *y;

double sums[1000000];
int f[1000000];
int l[1000000];

double opt(ll * a, int n){
	int ns = 0;
	for (int i = 0; i < n; i++) {
		// start new segment
		sums[ns] = a[i];
		f[ns] = i;
		l[ns] = i;
		while (ns > 0 && sums[ns]/(l[ns] - f[ns] + 1) < sums[ns-1]/(l[ns-1] - f[ns-1] + 1))
			sums[ns-1] += sums[ns], l[ns-1] = l[ns], ns--;
		ns++;
	}
	double v = 0;
	for (int i = 0; i < ns; i++) for (int j = f[i]; j <= l[i]; j++) {
		double d = sums[i]/(l[i] - f[i] + 1) - a[j];
		v += d*d;
	}
	return v;
}

int main(){
	int n; scanf("%d",&n);
	x = (ll*) calloc(n,sizeof(ll));
	y = (ll*) calloc(n,sizeof(ll));
	for (int i = 0; i < n; i++) scanf("%lld %lld", x+i, y+i);

	printf("%f\n", opt(x,n) + opt(y,n));
}