// Forward declaration of guess API.

// @param num, your guess

// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0

int guess(int num);

```
class Solution {
public:
int guessNumber(int n) {
int low,high,mid;
low=1;high=n;
while(low<=high)
{
mid=low+(high-low)/2;
if(guess(mid)==0)
return mid;
else if(guess(mid)==1)
high=mid-1;
else
low=mid+1;
}
return 0;
}
};
```