Codeforces Round #561 (Div. 2)

//A
#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int MAXN = 202020;
const int MOD = 998244353;
ll fac[MAXN],favin[MAXN];
ll quic(int a,int b){
	ll  ans = 1;
	for(;b;b>>=1,a=(ll)a*a%MOD){
		if((b&1)){
			ans=ans*a%MOD;
		}
	}
	return ans;
}
void init(){
	fac[0]=1;
	for(int i=1;i<=MAXN;i++)
		fac[i]=fac[i-1]*i%MOD;
	favin[MAXN]=quic(fac[MAXN],MOD-2);
	for(int i=MAXN;i>0;i--)
		favin[i-1] = favin[i]*i%MOD; 
	//1/(i-1)! =  1/(i!) * i;
}
ll C(int n,int m){
	if(n<0||m<0||m>n)return 0;
	return fac[n]*favin[m]%MOD*favin[n-m]%MOD; 
}
int main()
{
	init();
	int n;
	int q[400];
	memset(q,0,sizeof(q));
	cin>>n;
	while(n--){
		string s;
		cin>>s;
		q[s[0]]++;
	}
	ll ans = 0;
	for(char i = 'a';i<='z';i++ ){
		int nn = q[i]/2;
		ans+=C(nn,2);
		ans+=C(q[i]-nn,2);
	}
	cout<<ans<<endl;
	return 0;
}

//B
#include <bits/stdc++.h>
using namespace std;
char c[6] = {'a','e','i','o','u'};
int main()
{
	int k,n=-1,m=-1;
	scanf("%d",&k); 
	for(int i=5;i<=k/5;i++)
		for(int j=5;j<=k/5;j++)
		{
			if(i*j==k){
				n = i; m = j;
				break;
			}	
		}
	if(n<0&&m<0){
		printf("-1");return 0; 
	}
	for(int i=0;i<n;i++)
	{
		for(int j=0;j<m;j++)
		{
			printf("%c",c[(i+j)%5]);	
		}
	
	}
	return 0;
}

//C
#include <algorithm>
#include <iostream>
using namespace std;
int a[200005];
#define ll long long
int main()
{
	int n;
	scanf("%d",&n);
	for(int i=0;i<n;i++){
		int t;
		scanf("%d",&t);
		a[i] = abs(t);
	}
	sort(a,a+n);
	ll ans = 0;
	for(int i=0;i<n-1;i++){
		int add = lower_bound(a,a+n,2*a[i])- a;
		if(a[add]>2*a[i]){
			add=add-i-1;
		}else {
			while(a[add]==2*a[i]&&add<n){
				add++;
			}
			add--;
			add = add - i;
		}
		ans+=(ll)add;
	}
	cout<<ans;
 	return 0;	
}