class Solution {
    public int mySqrt(int x) {
        if (x == 1)
            return 1;
        int min = 0;
        int max = x;
        while (max-min > 1) {
            int m = (min+max)/2;
            if (x/m < m)
                max = m;
            else
                min = m;
        }
        return min;
    }
}