//2016.8.5
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>

using namespace std;

int A[105], B[105];
int dp[10005][16];
const int inf = 9999999;

int main()
{
    int L, N;
    while(cin>>L>>N)
    {
        for(int i = 0; i < L; i++)
          scanf("%d", &A[i]);
        for(int i = 0; i < L; i++)
            scanf("%d", &B[i]);
        memset(dp, inf, sizeof(dp));
        dp[1][1] = A[0];
        for(int i = 1; i < L*N; i++)
        {
            for(int j = 0; j < 15; j++)
            {
                int eng = j+1;
                if(eng == 15)eng = 10;
                dp[i+1][eng] = min(dp[i][j]+A[i%L], dp[i+1][eng]); 
                if(eng >= 5)dp[i+1][j-5] = min(dp[i][j]+B[i%L], dp[i+1][j-5]);
            }
        }
        int ans = inf;
        for(int i = 0; i < 15; i++)
          if(ans>dp[L*N][i])
            ans = dp[L*N][i];
        cout<<ans<<endl;
    }

    return 0;
}