PROBLEM_A: URAL 2024 Adventure Time

/*PROBLEM A : "UNSOLVED" */
/*TIME : ________________*/
#include "cstdio"
#include "cstring"
#include "cctype"
#include "algorithm"
#include "cmath"
#include "vector"
using namespace std;
#define Inc(i, a, b) for(int i = a; i < b; i++)
#define Dec(i, a, b) for(int i = a; i > b; i--)
#define Mem(a) memset(a, 0, sizeof(a))
#define Pii pair<int, int>
#define Pdd pair<double, double>
#define Cin scanf
#define Put printf
#define CIN(a) scanf("%d", &a)
#define CII(a, b) scanf("%d%d", &a, &b)
#define CIS(a) scanf("%s", a)
#define PUT(a) printf("%d\n", a)
#define PII(a, b) printf("%d %d\n", a, b)
#define PUS(a) printf("%s\n", a)
#define Pub push_back
#define Mpi make_pair
#define ll long long
#define maxn 100005
#define pi acos(-1)
#define eps 1e-10

char  st[maxn];
int n, k;
int is[27][2];
struct node {
int xc, no;
} ch[27];
bool comp(node a, node b) {
return a.no > b.no;
}
int C(int a, int b) {
int sum = 1;
Inc(i, 0, b) sum *= (a - i), sum /= i + 1;
return sum;
}
int main() {
while(~Cin("%s%d", st, &k)) {
n = strlen(st);
Mem(is), Mem(ch);
Inc(i, 0, 26) ch[i].xc = i, ch[i].xc = 0;
ch[26].no = -1;
Inc(i, 0, n) ch[st[i] - 'a'].no++;
sort(ch, ch + 26, comp);
int tmp = 1, num = 1;
Inc(i, 1, 27) {
if(ch[i].no == ch[i - 1].no) tmp++;
else {
is[num][0] = tmp, tmp = 1;
is[num++][1] = ch[i - 1].no;
}
if(ch[i].no == 0) break;
}
int it[27][2];
Mem(it);
Inc(i, 1, 27) {
it[i][0] += it[i - 1][0] + is[i][0];
it[i][1] += it[i - 1][1] + is[i][0] * is[i][1];
}
bool flag = 0;
Inc(i, 1, 27) {
if(it[i][0] >= k) {
int t = k - is[i - 1][0];
PII(it[i - 1][1] + t * is[i][1], C(is[i][0], t));
flag = 1;
break;
}
if(is[i][0] == 0) break;
}
if(!flag) PII(it[26][1], 1);
}
}