Lucky Word没大写，找了半天程序

#include<bits/stdc++.h>
using namespace std;
bool prime(int a)
{
    if(a<2)
        return false;
    if(a==2)
        return true;
    for(int i = 2;i*i<=a;i++)
        if(a%i==0)
            return false;
    return true;
}
int main()
{
    string a;
    cin>>a;
    int b[26] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
    for(int i = 0;i<a.size();i++)
        b[a[i]-'a']++;
    int maxn = 0,minn = 100;
    for(int i = 0;i<26;i++)
    {
        maxn = max(maxn,b[i]);
        if(b[i]!=0)
            minn = min(minn,b[i]);
    }
    if(prime(maxn-minn))
        cout<<"Lucky Word"<<endl<<maxn-minn;
    else
        cout<<"No Answer"<<endl<<0;
}