【链接】http://codeforces.com/contest/844/problem/A
【题意】
大水题
【题解】
看看不同的个数num是不是小于k,小于k,看看len-num够不够补的
【错的次数】
0
【反思】
貌似那种判断条件比较多的题都容易hack啊
【代码】
#include <bits/stdc++.h>
using namespace std;
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define LL long long
#define rep1(i,a,b) for (int i = a;i <= b;i++)
#define rep2(i,a,b) for (int i = a;i >= b;i--)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define ms(x,y) memset(x,y,sizeof x)
#define ri(x) scanf("%d",&x)
#define rl(x) scanf("%lld",&x)
#define rs(x) scanf("%s",x)
#define oi(x) printf("%d",x)
#define ol(x) printf("%lld",x)
#define oc putchar(' ')
#define os(x) printf(x)
#define all(x) x.begin(),x.end()
#define Open() freopen("F:\rush.txt","r",stdin)
#define Close() ios::sync_with_stdio(0)
typedef pair<int,int> pii;
typedef pair<LL,LL> pll;
const int dx[9] = {0,1,-1,0,0,-1,-1,1,1};
const int dy[9] = {0,0,0,-1,1,-1,1,-1,1};
const double pi = acos(-1.0);
const int N = 1e3;
int a[400];
char s[N+10];
int main(){
//Open();
//Close();
rs(s);
int len = strlen(s),num = 0;
int k;
ri(k);
rep1(i,0,len-1){
if (a[s[i]]==0) num++;
a[s[i]]++;
}
if (num >= k){
puts("0");
}else{
int need = k-num;
if (need <= len-num){
printf("%d
",need);
}else
puts("impossible");
}
return 0;
}