How to express with logic function, when A1 is greater than or equal to 50, A1 = 50, when A1 is less than 50, return the original value

How to express with logic function, when A1 is greater than or equal to 50, A1 = 50, when A1 is less than 50, return the original value

A1>=50?50:A1
perhaps
if(A1>=50){
A1=50;
}
Just leave it out