70 Climbing Stairs

You are climbing a stair case. It takes n steps to reach to the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
int climbStairs(int n) {
if (n == 0 || n == 1) return 1;
int a = 1, b = 1;
for (int i = 2; i <= n; i++) {
int tempB = b;
b = a + b;
a = tempB;
}
return b;
}