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

struct POINT
{
    float x,y;
};

int main(void)
{
    int n;
    struct POINT v[105];
    double A=0,P=0;
    scanf("%d", &n);
    for(int i=1; i<=n; i++)
        scanf("%f %f", &v[i].x, &v[i].y);

    for(int i=1; i<n; i++)
    {
        A+=0.5 * (v[i].x*v[i+1].y - v[i+1].x*v[i].y);
        P+=sqrt((v[i].x - v[i+1].x) * (v[i].x - v[i+1].x)+(v[i].y - v[i+1].y) * (v[i].y - v[i+1].y));
    }

    A+=0.5 * (v[n].x * v[1].y - v[1].x * v[n].y);
    A=abs(A);
    P+=sqrt((v[n].x - v[1].x) * (v[n].x - v[1].x)+ (v[n].y - v[1].y) * (v[n].y - v[1].y));

    printf("A=%f\n", A);
    printf("P=%f\n", P);
    return 0;
}