P4744 Iron man

f[i][j]=max(f[i-1][j],g[i][j]);
g[i][j]=max(f[i-2][j-1],g[i-1][j])+a[i];
h[i][j]=max(h[i-1][j],l[i][j]);
l[i][j]=max(l[i-1][j],h[i-2][j-1])+a[i];
ans=max(f[n][k],l[n][k+1]);

#include<bits/stdc++.h>
using namespace std;
#define int long long 
const int maxn=1e5+10;
int f[maxn][55],a[maxn],g[maxn][55];
int n,k;
signed main(){
    cin>>n>>k;
    for(int i=1;i<=n;i++)
        scanf("%lld",&a[i]);
    memset(f,-0x3f,sizeof(f));
    memset(g,-0x3f,sizeof(g));
    f[1][1]=g[1][1]=a[1];
    for(int i=0;i<=n;i++)
        f[i][0]=g[i][0]=0;
    for(int j=1;j<=k;j++)
        for(int i=2;i<=n;i++){
            f[i][j]=max(f[i-1][j],g[i-2][j-1])+a[i];
            g[i][j]=max(f[i][j],g[i-1][j]);
        }
    int ans=g[n][k];
    memset(f,-0x3f,sizeof(f));
    memset(g,-0x3f,sizeof(g));
    f[1][1]=g[1][1]=a[1];
    f[0][0]=0;
    for(int j=1;j<=k+1;j++)
        for(int i=2;i<=n;i++){
            f[i][j]=max(f[i-1][j],g[i-2][j-1])+a[i];
            g[i][j]=max(f[i][j],g[i-1][j]);
            //printf("%lld %lld %lld %lld\n",i,j,f[i][j],g[i][j]);
        }
    /*
    for(int i=1;i<=n;i++)
        a[i]+=a[i-1];
    for(int i=1;i<=n;i++)
        ans=max(ans,f[i][k]+a[n]-a[i]);
    */
    ans=max(ans,f[n][k+1]);
    printf("%lld\n",ans);
    return 0;
}