zoj 2122 A Flea on a Chessboard

#include <cstdio>#include <cstring>int s, x, y, dx, dy;bool judge (int a, int b) {    return (a%s) && (b%s) && ((a/s+b/s) % 2);}int main () {    while (scanf("%d%d%d%d%d", &s, &x, &y, &dx, &dy) == 5 && s + x + y + dx + dy) {        int i;        for (i = 0; i < 2 * s; i++) { if (judge (x, y)) {     printf("After %d jumps the flea lands at (%d, %d).n", i, x, y);     break; } x += dx; y += dy;        }        if (i == 2 * s) printf("The flea cannot escape from black squares.n");    }    return 0;}