/*
PROOF OF CORRECTNESS:
  EXP(X,Y): compute X^Y
*/
#include <stdio.h>

/* Note: this may get a warning because the return does not match
   a built-in exp function in C. Ignore the warning.
*/
int exp(int x, int y) {
int i, z;

  // PRE: x > 0 and y > 0

 
  z = x;


  i = 2;


  // INVARIANT: 
 
 
  while (i <= y) {
  
 
    z = z * x;
 
 
    i = i + 1;
 

  } // end while

  // INVARIANT:                                    and EXIT: 
  



  // POST: z = x^y

  return z;
}

int main() {
  printf("exp(2,4)=%d\n",exp(2,4));
  return 1;
}