Leetcode: sqrt (x)

#include <iostream>
using namespace std;
class Solution {
public:
int sqrt(int x) {
unsigned long long l = 0, r = x, mid;
unsigned long long multi;
while(l < r ) {
mid = (l+r) >> 1;
multi = mid * mid;
if(multi == x) {
return mid;
}else if(multi > x) {
r = mid -1;
}else {
l = mid + 1;
}
}
multi = l * l;
if(multi > x)
return l-1;
else
return l;
}
};

int main() {
Solution solution;
cout << solution.sqrt(2147395599) << endl;
return 0;
}