#include<map>

#include<set>

#include<cmath>

#include<queue>

#include<cstdio>

#include<vector>

#include<string>

#include<cstdlib>

#include<cstring>

#include<iostream>

#include<algorithm>

#define pb push_back

#define mp make_pair

#define Maxn 2002

#define Maxm 80002

#define LL __int64

#define Abs(x) ((x)>0?(x):(-x))

#define lson(x) (x<<1)

#define rson(x) (x<<1|1)

#define inf 0x7fffffff

#define Mod 1000000007

using namespace std;

int dp[Maxn][Maxn],val[];

char str[Maxn];

int main()

{

    int n,m,i,j,a,b;

    char s[];

   while(scanf("%d%d",&n,&m)!=EOF){

    scanf("%s",str+);

    for(i=;i<=n;i++){

        scanf("%s %d %d",s,&a,&b);

        val[s[]]=min(a,b);

    }

    for(i=;i<=m;i++){

        for(j=i-;j>=;j--){

            if(str[i]==str[j]){

                dp[j][i]=dp[j+][i-];

            }

            else{

                dp[j][i]=min(dp[j+][i]+val[str[j]],dp[j][i-]+val[str[i]]);

            }

        }

    }

    printf("%d\n",dp[][m]);

   }

    return ;

}