1015：计算并联电阻的阻值

#include <iostream>
#include <iomanip>
using namespace std;
int main(){
    float r1,r2;
    cin>>r1>>r2;
    cout<<setiosflags(ios::fixed)<<setprecision(2);
    cout<<1/((1/r1)+(1/r2))<<endl;
}