Tính chu vi và diện tích hình vuông

//Write a program that allows the user to enter the edge called a of the square and then calculates
//the perimeter and area of the square. The program must check whether the square edge is a
//positive number or not.
//Formula
//Perimeter = 4 * a
//Area = a * a
//Example 1: Please enter the edge of the square: -6
//The edge must be a positive number!
//Example 2: Please enter the edge of the square: 0
//The edge must be a positive number!
//Example 3: Please enter the edge of the square: 10
//The perimeter of the square is 40
//The area of the square is 100

#include <stdio.h>
#include <math.h>
int main() {
    int a, perimeter, area;
    printf("Please enter the edge of the square: ", a);
    scanf("%d", &a);
    perimeter = 4 * a;
    area = a * a;
    if (a < 0 || a == 0) {
        printf("The edge must be a positive number!\n", a);
    }
    else{
        printf("The perimeter of the square is %d\n", perimeter);
        printf("The area of the square is %d\n", area);
    }
    return 0;
}