The stupidest way is to count them one by one ~

According to the meaning of the question, insert the multiplication sign and divide it into one, two and three. All three situations are just (no insertion or more than four don't meet the meaning of the question)

A situation:

1×234=234

12×34=404

123×4=492

Two situations:

1×2×34=68

1×23×4=92

12×3×4= 144

Three situations:

1×2×3×4=24

The calculation shows that all seven numbers are different, so there are seven different results ~