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

int main() {
    float radius;
    
    printf("Enter the radius of the circle: ");
    scanf("%f", &radius);
    
    if (radius < 0 || radius > 50) {
        printf("Invalid Input\n");
    }else{
        
        float area = m_PI * radius * radius;
        printf("%.2f\n", area);
    }
    return 0;
}