不懂就问 编译失败

#include<bits/stdc++.h>
using namespace std;
int sum=0;
struct s{
	char k;
	int b;	
}a[27];
int main(){
	a={
		{'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',' '},
		{'1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','1','2','3','4','1','2','3','1','2','3','4','1'}
	};
	string str;
	getline(cin,str);
	for(int i=0;i<str.size();i++){
		sum+=a[(a.k).find(str[i])].b;
	}
	cout << sum;
	return 0;
}