#include<cstdio>#include<cstring>#include<string>#include<cmath>#include<vector>#include<queue>#include<algorithm>#include<set>using namespace std;int n,k,a[200010],sz;struct X{    int L,R,len;} s[200010];vector<int>v;int f[200010];bool cmp(X a, X b){    return a.len<b.len;}int main(){    scanf("%d%d",&n,&k);    for(int i=1; i<=n; i++) scanf("%d",&a[i]);    int sum=0; for(int i=1; i<=n; i++) if(a[i]<0) f[i]=1,sum++;    if(sum>k) printf("-1\n");    else    {        if(sum==0) printf("0\n");        else        {            for(int i=1; i<=n; i++) if(a[i]<0) v.push_back(i);            for(int i=0; i<v.size()-1; i++) s[sz].L=v[i], s[sz].R=v[i+1], s[sz].len = s[sz].R-s[sz].L-1, sz++;            sort(s,s+sz,cmp);            sum=k-sum;            for(int i=0; i<sz; i++)            {                if(sum>=s[i].len)                {                    for(int j=s[i].L;j<=s[i].R;j++) f[j]=1;                    sum=sum-s[i].len;                }            }            if(sum>=n+1-v[v.size()-1]-1)            {                for(int i=v[v.size()-1];i<=n;i++) f[i]=1;            }          //  for(int i=1;i<=n;i++) printf("%d ",f[i]);            int ans=0;            int f1=1,f2=n;            for(int i=1;i<=n;i++)            {                if(f[i]==0) continue;                else {f1=i;break;}            }            for(int i=n;i>=1;i--)            {                if(f[i]==0) continue;                else {f2=i;break;}            }            ans=ans+1;            if(f2!=n) ans=ans+1;            for(int i=f1+1;i<=f2;i++)            {                if(f[i]!=f[i-1]) ans++;            }            printf("%d\n",ans);        }    }    return 0;}