#include
using namespace std;
int n,k;
long long ans=0,a[2005],f[2005][2005];
int main()
{scanf("%d%d",&n,&k);for(int i=1;i<=n;i++){scanf("%lld",&a[i]);}for(int i=1;i<=n;i++){for(int j=0;j<=n;j++) f[i][j]=-1e18;}f[1][0]=0;for(int i=2;ifor(int j=0;j<=k;j++){f[i][j]=f[i-1][j];if(a[i]=1) f[i][j]=max(f[i][j],f[i-2][j-1]+min(a[i-1],a[i+1])-1);}}for(int i=0;i<=k;i++) ans=max(ans,f[n-1][i]);printf("%lld",ans);return 0;
}
