#include <stdio.h>                                                    // Q2005_1_assert.c
#include <assert.h>                          // See Textbook 13.10
int square(int k) { return k * k; }
void main(void) {
    int n = 22;
    int k = 0, d = 1, s = 1;
    while ( s <= n ) {     //@{}"//"   {@B {Loop invariant:}}
                               assert( d == 2 * k + 1           &&   s == square(k + 1)  );
        d = d + 2;
                               assert( d == 2 * (k + 1) + 1   &&   s == square(k + 1)  );
        s = s + d;
                               assert( d == 2 * (k + 1) + 1   &&   s == square(k + 2)  );
        k = k + 1;
                               assert( d == 2 * k + 1           &&   s == square(k + 1)  );
        printf("k = %d\t d = %d\t s = %d\n", k, d, s);
    }                          assert( s > n                        &&   s == square(k + 1)  );
    printf("The result is %d.\n", k);
}