#include <iostream>#include <algorithm>#include <cstdlib>#include <iostream>#include <algorithm>#include <cstdlib>#include <cstring>#include <string>#include <vector>#include <cstdio>#include <queue>#include <stack>#include <cmath>#include <time.h>#include <set>using namespace std;#define min(a,b) ((a)<(b)?(a):(b))#define max(a,b) ((a)>(b)?(a):(b))#define OUT #define LL __int64#define POW(x) (x)*(x)#define clr(x) memset(x,0,sizeof(x))#define eps 1e-3#define ee 2.7182818284590452354#define PI 3.1415926535897932384626433832795028 #define N 105#define M 100000009#define inf 1<<29double dp[33][33][205];double col[6];int len[6],l[6],r[6],m,n;vector<int> e[6];void init(){for(int i=0;i<5;i++) e[i].clear();for(int i=0;i<(1<<5);i++){int ans=0;for(int j=0;j<5;j++)if(i&(1<<j)) ans++;e[ans].push_back(i);}}void solve(){int i,j,k;dp[0][0][m]=0;for(int pp=0;pp<=n;pp++){for(int ii=0;ii<e[pp].size();ii++)for(int jj=0;jj<e[pp].size();jj++){for(i=0;i<n;i++){if((1<<i)&e[pp][ii]) continue;for(j=0;j<n;j++){if((1<<j)&e[pp][jj]) continue;int aa=(1<<i)|e[pp][ii];int bb=(1<<j)|e[pp][jj];for(int tt=m;tt>=l[i];tt--){for(k=l[i];k<=r[i];k++){if(tt<k) continue;if(dp[aa][bb][tt-k]>dp[e[pp][ii]][e[pp][jj]][tt]+col[j]*((double)(k*k)))dp[aa][bb][tt-k]=dp[e[pp][ii]][e[pp][jj]][tt]+col[j]*((double)(k*k));}}}}}}if(dp[(1<<n)-1][(1<<n)-1][0]==1.0*(inf)) printf("Impossiblen");else printf("%.3lfn",dp[(1<<n)-1][(1<<n)-1][0]);}int main(){int i,j,k;init();while(scanf("%d %d",&n,&m)==2){for(i=0;i<n;i++)scanf("%lf",&col[i]);for(j=0;j<n;j++)scanf("%d %d",&l[j],&r[j]);for(int i=0;i<(1<<n);i++)for(int j=0;j<(1<<n);j++)for(int k=m;k>=0;k--)dp[i][j][k]=1.0*(inf);solve();}return 0;}
