Three thieves' jokes

Suppose there are policemen a, b, c, thieves a, b, c,

First handcuff the thief at the starting point, and two policemen, A and B, take a boat to their destination: across the river;

A stays at the destination, B rows back to the starting point, takes A to the destination, and B rests at the destination to see thief A;

Change A back to the starting point to see thief C, and policeman C drives thief B to the destination;

Police c will monitor a and b at the destination, change b to the starting point, and change a to the thief c to the destination;

Policeman A stared at thieves A, B and C at the destination and rowed to the starting point to pick up policeman B instead of C. In order to maintain physical strength, policemen B and C rowed to the destination together.