def posicions_robot(it):
    px, py = 0, 0
    yield px, py
    for d, cm in it:
        if d == 'N':
            py = py + cm
        elif d == 'S':
            py = py - cm
        elif d == 'E':
            px = px + cm
        else:
            px = px - cm
        yield px, py