Solution:
/******************************************************************
*** Problem : ***
*** Author : Shipu Ahamed (Psycho Timekiller) ***
*** E-mail : [email protected] ***
*** University : BUBT,Dept. of CSE ***
*** Team : BUBT_Psycho ***
*** My Blog : http://shipuahamed.blogspot.com ***
*** Facebook : http://www.facebook.com/DeesheharaShipu ***
******************************************************************/
#include <list>
#include <set>
#include <map>
#include <ctime>
#include <stack>
#include <queue>
#include <cmath>
#include <deque>
#include <limits>
#include <string>
#include <cctype>
#include <cstdio>
#include <vector>
#include <bitset>
#include <numeric>
#include <cassert>
#include <sstream>
#include <fstream>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <complex>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <algorithm>
using namespace std;
#define sc scanf
#define pf printf
#define ll long long
#define pi 2*acos(0.0)
#define ull unsigned long long
#define all(v) v.begin(),v.end()
#define sii(t) scanf("%d",&t)
#define sll(t) scanf("%lld",&t)
#define ssii(a,b) scanf("%d%d",&a,&b)
#define ssll(a,b) scanf("%lld%lld",&a,&b)
#define Case(no) printf("Case %d: ",++no)
#define nl puts("")
#define P(a) printf("%d\n",a)
#define PL(a) printf("%lld\n",a)
#define PN(a) printf("%d ",a)
#define PLN(a) printf("%lld ",a)
#define CP(a) cout<<a<<endl;
#define CPN(a) cout<<a<<" ";
#define ff first
#define se second
#define pb push_back
#define ST(v) sort(all(v))
#define gcd(a,b) __gcd(a,b)
#define lcm(a,b) (a*(b/gcd(a,b)))
#define max3(a,b,c) max(a,max(b,c))
#define min3(a,b,c) min(a,min(b,c))
#define maxall(v) *max_element(all(v))
#define minall(v) *min_element(all(v))
#define cover(a,d) memset(a,d,sizeof(a))
#define popcount(i) __builtin_popcount(i) //count one
#define parity(i) __builtin_parity(i) //evenparity 0 and odd parity 1
#define input freopen("in.txt","r",stdin)
#define output freopen("out.txt","w",stdout)
#define un(v) ST(v), (v).earse(unique(all(v)),v.end())
#define common(a,b) ST(a), ST(b), a.erase(set_intersection(all(a),all(b),a.begin()),a.end())
#define uncommon(a,b) ST(a), ST(b), a.erase(set_symmetric_difference(all(a),all(b),a.begin()),a.end())
////============ CONSTANT ===============////
#define mx (2000010)
#define inf 1<<30 //infinity value
#define eps 1e-9
#define mod 10007
////=====================================////
int main()
{
int t;
sii(t);
while(t--)
{
ll s;
sll(s);
PL((ll)((-1)+sqrt(1+(8*s)))/2);
}
return 0;
}
https://github.com/Shipu/OnlineJudgeProblemSolutionWithCPlusPlus/tree/master/uva/11614/11614.cpp