Codeforces 192 A.Funky Numbers

#include<bits/stdc++.h>
using namespace std;

typedef long long LL;
typedef vector<LL>vll;
typedef map<LL, bool>mpbl;

#define high 1000000000
#define fast ios_base::sync_with_stdio(false)

int len=0;
vll v;
mpbl mp;

void funkey()
{
    LL i;

    for(i=1; ; i++)
    {
        if(((i * (i+1)) / 2 ) > high)
        {
            //cout << i << " " << i+1;
            break;
        }

        v.push_back(((i * (i+1)) / 2));
        mp[((i * (i+1)) / 2)] = true;
    }

    //for(i=0; i<50; i++) cout << v[i] << " ";

    len = v.size();
}

int khoj(int lo, int hi, LL itm)
{
    int mid;

    while(lo <= hi)
    {
        mid = (lo + hi) / 2;

        if(v[mid] == itm) return mid;
        else if(v[mid] > itm) hi = mid - 1;
        else if(v[mid] < itm) lo = mid + 1;
    }

    return lo;
}

int main()
{
    fast;
    funkey();
    LL n;
    while(cin >> n)
    {
        int r = khoj(0, len-1, n);

        if(v[r] != n)
        {
            r--;

        }

        LL d;
        bool f=false;

        for(int i=0; i<=r; i++)
        {
            d = n - v[i];

            if(mp[d])
            {
                cout << "YES\n";
                f=true;
                break;
            }
        }

        if(!f) cout << "NO\n";
    }

    return 0;
}