Sum

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fr first
#define sc second
#define pb push_back
#define mp make_pair
#define forr(i,a,b) for(ll i=a;i<b;i++)
#define mod 100000007
#define eps 0.0000001

int main(){ll ans=0,n;
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
cin>>n;
forr(i,1,n)
forr(j,i+1,n)
forr(z,j+1,n)
if(i+j+z==n)ans++;
cout<<ans<<endl;
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