记一下STL的一个题

A. Diversity

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Calculate the minimum number of characters you need to change in the string s, so that it contains at least k different letters, or print that it is impossible.

String s consists only of lowercase Latin letters, and it is allowed to change characters only to lowercase Latin letters too.

Input

First line of input contains string s, consisting only of lowercase Latin letters (1 ≤ |s| ≤ 1000, |s| denotes the length of s).

Second line of input contains integer k (1 ≤ k ≤ 26).

Output

Print single line with a minimum number of necessary changes, or the word «impossible» (without quotes) if it is impossible.

Examples

input

yandex
6

output

0

input

yahoo
5

output

1

input

google
7

output

impossible

#include <iostream>
#include<string>
#include<set>
#include<algorithm>
using namespace std; 
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
//set<int>ff; 
int main(int argc, char** argv) {
    set<int>ff; 
    string s;
    int k;
    cin>>s;
    cin>>k;
    int len=s.size() ;
    
 for(int i=0;i<len;i++)  
    {  
        ff.insert(s[i]);  
    }  
    if(len<k)  
        printf("impossible
");  
    else  
    {  
        int w=ff.size();  
        if(w>=k)  
            printf("0
");  
        else  
            printf("%d
",k-w);  
    }  
    return 0;  
}