Using promela and Spin to solve algorithmic puzzle about frogs

Question

I study verification at the university using promela. And as an example, i need to solve algorithmic puzzle about frogs. I tried to solve the problem but something doesn't work right

In how many moves will the frogs exchange places? Frogs jump in turn on an empty cage when it is nearby or through one frog of the opposite color. enter image description here

bool    all_frog_done;
active proctype frog_jump()
{
byte i = 0;
byte position[7];
position[0] = 1;
position[1] = 1;
position[2] = 1;
position[3] = 0;
position[4] = 2;
position[5] = 2;
position[6] = 2;
all_frog_done = false;
printf("MSC: position[0] %d position[1] %d position[2] %d position[3] %d position[4] %d position[5] %d position[6] %d \n", position[0], position[1], position[2], position[3], position[4], position[5], position[6]);
do
:: (position[0] == 2) && (position[1] == 2) && (position[2] == 2) && (position[3] == 0) && (position[4] == 1) && (position[5] == 1) && (position[6] == 1) ->
all_frog_done = true; break;
:: else ->
if 
:: (position[i] == 1) && (position[i+1] == 0) && (i != 6)  -> 
    position[i] = 0;
    position[i+1] = 1;
:: (position[i] == 2) && (position[i-1] == 0) && (i != 0)  -> 
    position[i] = 0;
    position[i-1] = 2;
:: (position[i] == 1) && (position[i+1] == 2) && (position[i+2] == 0)  && (i <= 4)-> 
    position[i] = 0;
    position[i+2] = 1;
:: (position[i] == 2) && (position[i-1] == 1) && (position[i-2] == 0)  && (i >= 2)-> 
    position[i] = 0;
    position[i-2] = 2;
fi;
printf("MSC: position[0] %d position[1] %d position[2] %d position[3] %d position[4] %d position[5] %d position[6] %d \n", position[0], position[1], position[2], position[3], position[4], position[5], position[6]);
if
        :: (i < 7) -> i++;
        :: (i > 0) -> i--;
fi;
od;

}