Sum

/** MIT License Copyright (c) 2018-2019(!) Vasilyev Daniil **/
#include <bits/stdc++.h>
using namespace std;
template<typename T> using v = vector<T>;
#define int long long
typedef long double ld;
typedef string str;
typedef vector<int> vint;
#define rep(a, l, r) for(int a = (l); a < (r); a++)
#define pb push_back
#define fs first
#define sc second
#define sz(a) ((int) a.size())
const long long inf = 4611686018427387903; //2^62 - 1
#if 0  //FileIO
const string fileName = "";
ifstream fin ((fileName == "" ? "input.txt"  : fileName + ".in" ));
ofstream fout((fileName == "" ? "output.txt" : fileName + ".out"));
#define get fin >>
#define put fout <<
#else
#define get cin >>
#define put cout <<
#endif
#define eol put endl
void read() {} template<typename Arg,typename... Args> void read (Arg& arg,Args&... args){get (arg)     ;read(args...) ;}
void print(){} template<typename Arg,typename... Args> void print(Arg  arg,Args...  args){put (arg)<<" ";print(args...);}
int getInt(){int a; get a; return a;}
//code starts here
void run() {
    int n;
    get n;
    int ans = 0;
    rep(a, 1, n)
        rep(b, a + 1, n) {
            int c = n - a - b;
            if (c > b)
                ans++;
        }
    put ans;
}
signed main() {srand(time(0)); ios::sync_with_stdio(0); cin.tie(0); put fixed << setprecision(12); run(); return 0;}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED