Not good at code, But i will try my best.

include <iostream>

using namespace std;
const int nm = 1e6 + 1;
int n, a[nm], i, dem, j;
int main () {
freopen("TONGBANGKHONG.INP","r",stdin);
freopen("TONGBANGKHONG.OUT","w",stdout);
cin >> n;
for (i = 0; i < n; i++)
cin >> a[i];
dem = 0;
for(i=0; i<n-1; i++)
for (j=i+1;j<n;j++)
if(a[i] + a[j] == 0)
dem++;
if (dem == 0)
cout << 0;
else
cout << dem << endl;
return 0;
}

2023 - n : YOU-TM

ủa alo bạn ơi

https://readme-typing-svg.demolab.com/?font=Fira+Code&size=30&pause=1000&color=F7AF5E&background=FF0000&random=false&width=435&lines=Khoa+is+the+best;You+are+king+too

include <bits/stdc++.h>

define ll long long

define N 1000005

using namespace std;
ll n,k;
ll a[N3],c[N3];
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
// freopen("STEP.INP","r",stdin);
// freopen("STEP.OUT","w",stdout);
cin>>n>>k;
for(ll i=1;i<=k;i++){
cin>>a[0];
a[a[0]]=1;
}
c[0]=1;
c[1]=1;
for(ll i=2;i<=n;i++){
if(a[1]==1) c[1]=0;
if(a[i]==0) c[i]=(c[i-1]+c[i-2])%13051984;
}
cout<<c[n];
return 0;
}