Thread: How to terminate in loop? Help

Code:

  float i, R, I; // counter, resistance, input//
        float V; // voltage//


        printf("Enter the current: ");
        scanf("%f",&I);






        while ( R != -1) {


                 
                printf("Enter the resistance: " );
                scanf("%f",&R);
                V= R * I;
                printf("Voltage is %f\n", V);
        }


        return 0;

The question is to write a program that will input resistance R, current I for serval resistors, and will calculate and display the voltage for each resistor. The loop will terminate if your enter -1 as the resistance value. (Note that your program should output nothing when -1 is entered as the resistance value)
I want it to do nothing when I enter -1 for resistance but for this one it calculates the voltage. So what should i do?