I have column with following Observations:

```
SSD
C2ES
M1 SSD
M1 C2ES

```

I want my final output like 

```
SSD
C2ES
SSD
C2ES

```

I used the following code:

```
data dataset;
set dataset;
if substr(filiere,1,3) = 'M1 ' then filiere = substr(filiere,1,3);
run;

```

It removes 3 symbols from the end, what should I change in order to make it in right direction and if space is counted?

Thanks in advance!