everest% cc scan4.c
everest% 

everest% a.out 
Enter an integer: 3
r = 1 c = 3
Enter an integer: 4
r = 1 d = 4
everest% 

everest% a.out
Enter an integer: 3 4
r = 1 c = 3
Enter an integer: r = 1 d = 4
everest% 

everest% a.out
Enter an integer: abc
r = 0 c = 0
Enter an integer: r = 0 d = 0
everest%