/**
knakul853
**/
class Solution {
public:
    int mySqrt(int x) {

        int l = 0, h = x;
        long long ans = 0;
        while(l <= h)
        {
            long long mid = l + ( h - l)/2;

            if(mid * mid >= x)ans = mid, h = mid-1;
            else l = mid+1;
        }

        if(  ans * ans == (long long)x) return ans;
        return ans-1;

    }
};