#include <stdio.h>

int main()
{
    FILE *fp1, *fp2;
    float r, area;

    fp1 = fopen("input.txt", "r");
    fp2 = fopen("output.txt", "w");

    fscanf(fp1, "%f", &r);

    area = 3.14 * r * r;

    fprintf(fp2, "%.2f", area);

    fclose(fp1);
    fclose(fp2);

    return 0;
}