#include #define all(v) v.begin(), v.end() #define rall(v) v.rbegin(), v.rend() #define rep(i,n) for(int i=0;i<(int)(n);i++) #define drep(i,j,n) for(int i=0;i<(int)(n-1);i++)for(int j=i+1;j<(int)(n);j++) #define trep(i,j,k,n) for(int i=0;i<(int)(n-2);i++)for(int j=i+1;j<(int)(n-1);j++)for(int k=j+1;k<(int)(n);k++) #define codefor int test;scanf("%d",&test);while(test--) #define INT(...) int __VA_ARGS__;in(__VA_ARGS__) #define LL(...) ll __VA_ARGS__;in(__VA_ARGS__) #define yes(ans) if(ans)printf("yes\n");else printf("no\n") #define Yes(ans) if(ans)printf("Yes\n");else printf("No\n") #define YES(ans) if(ans)printf("YES\n");else printf("NO\n") #define popcount(v) __builtin_popcountll(v) #define vector2d(type,name,h,...) vector>name(h,vector(__VA_ARGS__)) #define vector3d(type,name,h,w,...) vector>>name(h,vector>(w,vector(__VA_ARGS__))) #define vector4d(type,name,h,w,d,...) vector>>>name(h,vector>>(w,vector>(d,vector(__VA_ARGS__)))) using namespace std; using ll = long long; template using rpriority_queue = priority_queue, greater>; const int MOD=1000000007; const int MOD2=998244353; const int INF=1<<30; const ll INF2=1LL<<60; void scan(int& a){scanf("%d",&a);} void scan(long long& a){scanf("%lld",&a);} templatevoid scan(pair& p){scan(p.first);scan(p.second);} templatevoid scan(tuple& p){scan(get<0>(p));scan(get<1>(p));scan(get<2>(p));} template void scan(array& a){ for(auto&& i : a) scan(i);} template void scan(T& a){cin>>a;} template void scan(vector& vec){for(auto&& it:vec)scan(it);} void in(){} template void in(Head& head, Tail&... tail){scan(head);in(tail...);} void print(const int& a){printf("%d",a);} void print(const long long& a){printf("%lld",a);} void print(const double& a){printf("%.15lf",a);} templatevoid print(const pair& p){print(p.first);putchar(' ');print(p.second);} template void print(const T& a){cout< void print(const vector& vec){if(vec.empty())return;print(vec[0]);for(auto it=vec.begin();++it!= vec.end();){putchar(' ');print(*it);}} void out(){putchar('\n');} template void out(const T& t){print(t);putchar('\n');} template void out(const Head& head,const Tail&... tail){print(head);putchar(' ');out(tail...);} template void dprint(const T& a){cerr< void dprint(const vector& vec){if(vec.empty())return;cerr< void debug(const T& t){dprint(t);cerr< void debug(const Head& head, const Tail&... tail){dprint(head);cerr<<" ";debug(tail...);} ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; } struct dsu { public: dsu() : _n(0) {} dsu(int n) : _n(n), parent_or_size(n, -1) {} int merge(int a, int b) { assert(0 <= a && a < _n); assert(0 <= b && b < _n); int x = leader(a), y = leader(b); if (x == y) return x; if (-parent_or_size[x] < -parent_or_size[y]) std::swap(x, y); parent_or_size[x] += parent_or_size[y]; parent_or_size[y] = x; return x; } bool same(int a, int b) { assert(0 <= a && a < _n); assert(0 <= b && b < _n); return leader(a) == leader(b); } int leader(int a) { assert(0 <= a && a < _n); if (parent_or_size[a] < 0) return a; return parent_or_size[a] = leader(parent_or_size[a]); } int size(int a) { assert(0 <= a && a < _n); return -parent_or_size[leader(a)]; } std::vector> groups() { std::vector leader_buf(_n), group_size(_n); for (int i = 0; i < _n; i++) { leader_buf[i] = leader(i); group_size[leader_buf[i]]++; } std::vector> result(_n); for (int i = 0; i < _n; i++) { result[i].reserve(group_size[i]); } for (int i = 0; i < _n; i++) { result[leader_buf[i]].push_back(i); } result.erase( std::remove_if(result.begin(), result.end(), [&](const std::vector& v) { return v.empty(); }), result.end()); return result; } private: int _n; // root node: -1 * component size // otherwise: parent std::vector parent_or_size; }; int main(){ INT(n); vector a(n); in(a); dsu uf(n); for(int i = 0; i + 1 < n; i++){ if(a[i] >= 1 && a[i + 1] >= 1){ //if(a[i] % 2 == 1 && a[i + 1] == 1)continue; uf.merge(i, i + 1); } } auto G = uf.groups(); for(auto &&vec:G){ ll s1 = 0, s2 = 0; sort(all(vec)); if(a[vec[0]]==0)continue; for(int i = 0; i < vec.size(); i+= 2){ s1 += a[vec[i]]; } for(int i = 1 ; i < vec.size(); i+=2){ s2 += a[vec[i]]; } if(s1 != s2){ out("No"); return 0; } bool flag = false; for(int i = 0; i + 1 < vec.size(); i++){ if(a[vec[i]] % 2 == a[vec[i+1]] % 2){ flag = true; break; } } if(!flag){ out("No"); return 0; } flag = true; int v = 0, cnt = 0; for(int i = 1; i + 1 < vec.size(); i++){ if(a[vec[i]] % 2 == 1){ if(a[vec[i]-1] % 2 == 1 && a[vec[i]+1] % 2 == 1){ flag = false; break; } } } if(!flag){ out("No"); return 0; } } out("Yes"); }