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47 lines
1.1 KiB (Stored with Git LFS)
C++
47 lines
1.1 KiB (Stored with Git LFS)
C++
#include<bits/stdc++.h>
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using namespace std;
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#define rep(i,x,y) for (int i=(x);i<=(y);i++)
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#define drep(i,y,x) for (int i=(y);i>=(x);i--)
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#define pii pair<int,int>
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#define fir first
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#define sec second
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#define MP make_pair
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#define templ template<typename T>
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templ bool chkmin(T &x,T y){return x>y?x=y,1:0;}
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templ bool chkmax(T &x,T y){return x<y?x=y,1:0;}
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void file() {
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#ifdef NTFOrz
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freopen("a.in","r",stdin);
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#endif
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}
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typedef long long ll;
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#define mod 1000000007ll
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#define sz 101010
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int n,m;
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int a[sz];
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ll pw[sz];
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ll SS(ll n){return n*(n-1)/2%mod;}
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int main() {
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cin>>n>>m;
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ll S=0;
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rep(i,1,n) cin>>a[i],(S+=a[i])%=mod;
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pw[0]=1; rep(i,1,sz-1) pw[i]=pw[i-1]*2%mod;
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ll ans=0;
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rep(i,1,m) {
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ll sum=S*pw[i-1]%mod;
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ll W=sum*(n*pw[i]%mod+1)%mod;
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sum=sum*2%mod;
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ll res=W*pw[m-i]%mod+sum*SS(pw[m-i])%mod*pw[i]%mod*n%mod;
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chkmax(ans,res%mod);
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}
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ll sum=S;
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ll W=0; rep(i,1,n) (W+=1ll*a[i]*(n-i+1)%mod)%=mod;
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ll res=W*pw[m]%mod+sum*SS(pw[m])%mod*n%mod;
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chkmax(ans,res%mod);
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cout<<ans;
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return 0;
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}
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