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

int main() {
    float radius, area;
    printf("Enter the radius: ");
    scanf("%f", &radius);
    
    if (radius >= 0) {
        area = M_PI * radius * radius;
        printf("%.2f\n", area);
    } else {
        printf("Invalid Input");
    }
    
    return 0;
}