Find the time complexity of sum of two numbers

What is the time complexity of the program for the sum of two numbers ?

Step count method

void main() 
{
int a,b,c; //———-0
a=10; //———-1
b=20; //———-1
c=a+b; //———-1
}
f(n) = 0+1+1+1 = 3
f(n) = O(1)