How to define minimum value for given number? I want to say minimum value for X is 1000. now X can be anything. so M would be the multiplier of X so that M*X >= 1000. What would be the mathematic way of doing this without using if statement?
M = 1;
X = 1000;
if(X < 1000) M = 1000/X;
X = M*X;

I want something like 
$M = 1000/X$
$X = M*X;$
But this means X is always 1000. its not minimum.
I'm just being curios of what could be the expression without if statement.

If you want to ensure that $X$ isn't lower than $1000$, using a multiplier is a contrived way* to achieve it.
Just write
$$X\leftarrow\max(X,1000).$$

The contrived way
You want to ensure
$$MX\ge1000$$ so that
$$M\ge\frac{1000}X.$$
Then you can take the multiplier
$$\max\left(1,\frac{1000}X\right)$$
and assign
$$X\leftarrow X*\max\left(1,\frac{1000}X\right).$$
