题干：
As you very well know, this year's funkiest numbers are so called triangular numbers (that is, integers that are representable as , where k is some positive integer), and the coolest numbers are those that are representable as a sum of two triangular numbers.
A well-known hipster Andrew adores everything funky and cool but unfortunately, he isn't good at maths. Given number n, help him define whether this number can be represented by a sum of two triangular numbers (not necessarily different)!
Input
The first input line contains an integer n (1 ≤ n ≤ 109).
Output
Print "YES" (without the quotes), if n can be represented as a sum of two triangular numbers, otherwise print "NO" (without the quotes).
Examples
Input
256
Output
YES
Input
512
Output
NO
Note
In the first sample number .
In the second sample number 512 can not be represented as a sum of two triangular numbers.
题目大意：
给你一个数字N，问你是否存在两个数字A,B使得N=A(A+1)2+B(B+1)2N=A(A+1)2+B(B+1)2
解题报告：
优秀的二分，复杂度sqrtnlogn
#include<bits/stdc++.h>using namespace std;int main()
{int n;cin>>n;int tmp,key;int l ,r,mid;n*=2;for(int i = 1; i<=sqrt(n); i++) {tmp = i * (i+1);key = n-tmp;l = i;r = sqrt(n);while(l<=r) {mid = (l+r)/2;if(mid * (mid+1) < key) l=mid+1;else if(mid*(mid+1)>key) r = mid-1;else {printf("YES\n");return 0 ;}}}printf("NO\n");return 0 ;
}
