A

# include <bits/stdc++.h>
using namespace std;

int x,y,z;

int main() {
	cin >> x >> y >> z;
	if (x + y == z || x + z == y || y + z == x) cout << "true";
	else cout << "false";
} 

B

#include<bits/stdc++.h>

using namespace std;

int n,a[1010],ans;
long long sum;

int main(){
	cin >> n;
	for (int i=1; i<=n; ++i) cin >> a[i];
	sort(a+1, a+n+1);
	for (int i=1; i<=n; ++i) {
		if (sum < a[i]) ans++, sum += a[i];
	}
	cout << ans;
	return 0;
}

C

#include<bits/stdc++.h>

using namespace std;

int n,k,ans=1000000,d[1000010];
char s[1000010];

int main(){
	cin >> n >> k;
	cin >> s+1;
	for (int i=1; i<=n; ++i) d[i] = d[i-1] + (s[i] == 'L');
	for (int i=k; i<=n; ++i) ans = min(ans, d[i] - d[i-k]);
	cout << ans;
	return 0;
}

D

#include<bits/stdc++.h>

using namespace std;

int ans,n,a[20];
bool v[20];

bool check(int x) {
	if (x <= 1) return false;
	for (int i=2; i*i<=x; ++i) if (x%i == 0) return false;
	return true;
}

void dfs(int x) {
	
	if (x == n+1) {
		ans++;
		return; 
	}
	
	for (int i=1; i<=n; ++i) {
		if (v[i]) continue;
		if (x > 1 && check(a[x-1]+i)) continue;
		v[i] = 1;
		a[x] = i;
		dfs(x+1);
		v[i] = 0;
	}
}

int main(){
	cin >> n;
	dfs(1);
	cout << ans;
	return 0;
}

E

#include<bits/stdc++.h>

using namespace std;

char s[1000010];
int n,t[30]; 
long long ans;

int main(){
	cin >> s;
	n = strlen(s);
	for (int i=0; i<n; ++i) {
		t[s[i]-'a']++;
		ans += t[s[i]-'a'];
	}
	cout << ans;
	return 0;
}