<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def solve(self):
 """ Solve the pair. """

        cycle = ["FR", "RB", "BL", "LF"]
        combine = self.combine()
        put = Formula(Step("y") * cycle.index(self.pair) or [])
        self.cube(put)
        self.pair = "FR"
        estimated = self.estimated_position()
        for U_act in [Formula(), Formula("U"), Formula("U2"), Formula("U'")]:
            self.cube(U_act)
            for put_act in [Formula("R U R'"), Formula("R U' R'"), Formula("R U2 R'"), 
                            Formula("F' U F"), Formula("F' U' F"), Formula("F' U2 F")]:
                self.cube(put_act)
                if self.get_pair() == estimated:
                    return combine + put + U_act + put_act
                self.cube(put_act.reverse())
            self.cube(U_act.reverse())