
ZOJ Problem Set  2305
A Compiler Mystery: We are given a Clanguage style for loop of type for (variable = A; variable != B; variable += C) I.e., a loop which starts by setting variable to value A and while variable is not equal to B, repeats statement followed by increasing the variable by C. We want to know how many times does the statement get executed for particular values of A, B and C, assuming that all arithmetics is calculated in a kbit unsigned integer type (with values 0 <= x < 2k) modulo 2k. Input The input consists of several instances. Each instance is described by a single line with four integers A, B, C, k separated by a single space. The integer k (1 <= k <= 32) is the number of bits of the control variable of the loop and A, B, C (0 <= A, B, C < 2k) are the parameters of the loop. The input is finished by a line containing four zeros. Output The output consists of several lines corresponding to the instances on the input. The ith line contains either the number of executions of the statement in the ith instance (a single integer number) or the word FOREVER if the loop does not terminate. Sample Input
3 3 2 16 Sample Output
0 Source: Czech Technical University Open 2004 