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# 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;
}
```