A wise man told Kerem "Different is good" once, so Kerem wants all things in his life to be different.
Kerem recently got a string s consisting of lowercase English letters. Since Kerem likes it when things are different, he wants all substrings of his string s to be distinct. Substring is a string formed by some number of consecutive characters of the string. For example, string "aba" has substrings "" (empty substring), "a", "b", "a", "ab", "ba", "aba".
If string s has at least two equal substrings then Kerem will change characters at some positions to some other lowercase English letters. Changing characters is a very tiring job, so Kerem want to perform as few changes as possible.
Your task is to find the minimum number of changes needed to make all the substrings of the given string distinct, or determine that it is impossible.
Input
The first line of the input contains an integer n (1 ≤ n ≤ 100 000) — the length of the string s.
The second line contains the string s of length n consisting of only lowercase English letters.
Output
If it's impossible to change the string s such that all its substring are distinct print -1. Otherwise print the minimum required number of changes.
Examples
Input
2 aa
Output
1
Input
4
koko
Output
2
Input
5
murat
Output
0
Note
In the first sample one of the possible solutions is to change the first character to 'b'.
In the second sample, one may change the first character to 'a' and second character to 'b', so the string becomes "abko".
题目分析，就是找有多少个字母重复，如果输入字母大于26，就输出-1，否则就判断重复的字母有几个答案就是这个统计数。
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上ac代码。
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学习算法
#include<iostream> #include<algorithm> #include<cstring> using namespace std; int main() { int t;cin>>t;int d=0; char a[1000000];int b[300]; for(int i=1;i<=t;i++) { cin>>a[i]; } for(int i=1;i<=26;i++) { b[i]=0; } if(t>26) { cout<<"-1"<<endl; return 0; } else { for(int i=1;i<=t;i++) { if(b[a[i]-'A'+1]==0) b[a[i]-'A'+1]=1; else d++; } } cout<<d<<endl; }
