#include <stdio.h>

int main() {

    int r1, r2;
    scanf("%d %d", &r1, &r2);

    float r, me;
    me = (1.0 / r1 + 1.0 / r2);
    r = 1 / me;
    
    printf("%.1f\n", r);

    return 0;

}