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

const float PI = 3.1416;

float laske_sektorin_ala(float sade, float kulma) {
    return  PI * pow(sade, 2) * kulma / 360;
}

int main() {
    printf("%f\n", laske_sektorin_ala(5));
    return 0;
}