#include #include #include #include #include #include #include using namespace std; #define int long long #define endl "\n" constexpr long long INF = (long long)1e18; constexpr long long MOD = 1'000'000'007; struct fast_io { fast_io(){ std::cin.tie(nullptr); std::ios::sync_with_stdio(false); }; } fio; class union_find { int _setnum; vector par, nume; public: union_find(){ } union_find(int x){ par.resize(x); nume.resize(x); init(); } ~union_find(){ // } void clear(){ _setnum = 0; par.clear(); nume.clear(); } void init(){ _setnum = par.size(); for(int i = 0; i < par.size(); i++){ par[i] = i; nume[i] = 1; } } void resize(int x){ par.resize(x); nume.resize(x); init(); } int find(int x){ return par[x] == x ? x : par[x] = find(par[x]); } void unite(int x, int y){ x = find(x); y = find(y); if(x == y)return; _setnum--; if(nume[x] > nume[y]) std::swap(x,y); par[x] = y; nume[y] += nume[x]; } bool same(int x, int y){ return find(x) == find(y); } int numel(int x){ return nume[find(x)]; } int size(){ return par.size(); } int setnum(){ return _setnum; } }; signed main(){ cout< A; union_find uf; cin>>N>>K; K--; A.resize(N); uf.resize(N); for(int i = 0; i < N; i++){ cin>>A[i]; if(i && A[i-1] && A[i]) uf.unite(i-1, i); } for(int i = K+1; i < N; i++){ if(uf.same(i, K)) r += A[i]; if(A[i] == 1) break; } for(int i = K-1; i >= 0; i--){ if(uf.same(i, K)) l += A[i]; if(A[i] == 1) break; } if(A[K] == 0) ans = 0; else if(A[K] == 1) ans = A[K] + max(r, l); else ans = A[K] + r + l; cout<