#include <iostream>
using namespace std;
int main(){
double R,R0,R1,R2,R3;
cout << "R1: ";
cin >> R1;
cout << "R2: ";
cin >> R2;
cout << "R3: ";
cin >> R3;
R0 = 1/R1+1/R2+1/R3;
R = 1/R0;
cout << "R = " << R;
return 0;
}
#include <iostream>
using namespace std;
int main(){
double R,R0,R1,R2,R3;
cout << "R1: ";
cin >> R1;
cout << "R2: ";
cin >> R2;
cout << "R3: ";
cin >> R3;
R0 = 1/R1+1/R2+1/R3;
R = 1/R0;
cout << "R = " << R;
return 0;
}