261

//261
#include <cstdio>
#include <cmath>

int main(void) {
    FILE* fin = fopen("input.txt", "r");
    FILE* fout = fopen("output.txt", "w");

    double a, b, f1, f2, f3;
    fscanf(fin, "%lf%lf", &a, &b);
    fclose(fin);
    f1 = (a + b) / 2;
    f2 = sqrt(a * b);
    f3 = sqrt(f1 * f2);

    fprintf(fout, "%.2f\n", f3);
    fclose(fout);
    return 0;
}