n,k=list(map(int,input().split()))
s=input()
a=list(map(str,input().split()))
d,f,p={},"",0
for i in range(k):
d[a[i]]=1
for i in range(n):
if d.get(s[i])!=None:
f+=s[i]
else:
g=len(f)
p+=(g*(g+1))//2
f=""
if f:
g=len(f)
p+=(g*(g+1))//2
print(p)#include<bits/stdc++.h>
using namespace std;
long long i,k,m,n,t,p[27];
char x;
string s;
int main(){
for(cin>>n>>k>>s;k--;p[x-96]=1)
cin>>x;
for(;i<=n;i++)
i<n&&p[s[i]-96]?m++:(t+=m*(m+1)/2,m=0);
cout<<t;
return 0;
}
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