#include // c #include // io #include #include #include #include // container #include #include #include #include #include #include #include // other #include #include #include #include #include using namespace std; typedef long long ll;typedef unsigned long long ull;typedef long double ld; #define ALL(c) c.begin(),c.end() #define IN(l,v,r) (l<=v && v < r) template void UNIQUE(T& v){v.erase(unique(ALL(v)),v.end());} //debug== #define DUMP(x) cerr << #x <<" = " << (x) #define LINE() cerr<< " (L" << __LINE__ << ")" struct range{ struct Iter{ int v,step; Iter& operator++(){v+=step;return *this;} bool operator!=(Iter& itr){return vitr.v;} int& operator*(){return v;} }; Iter i, n; rrange(int i, int n,int step):i({i-1,step}), n({n-1,step}){} rrange(int i, int n):rrange(i,n,1){} rrange(int n) :rrange(0,n){} Iter& begin(){return n;} Iter& end(){return i;} }; //input template istream& operator >> (istream& is,pair& p){return is>>p.first>>p.second;} template istream& operator >> (istream& is,tuple& t){return is >> get<0>(t);} template istream& operator >> (istream& is,tuple& t){return is >> get<0>(t) >> get<1>(t);} template istream& operator >> (istream& is,tuple& t){return is >>get<0>(t)>>get<1>(t)>>get<2>(t);} template istream& operator >> (istream& is,tuple& t){return is >> get<0>(t)>>get<1>(t)>>get<2>(t)>>get<3>(t);} template istream& operator >> (istream& is,vector& as){for(int i:range(as.size()))is >>as[i];return is;} //output template ostream& operator << (ostream& os, const set& ss){for(auto a:ss){if(a!=ss.begin())os<<" "; os< ostream& operator << (ostream& os, const pair& p){return os< ostream& operator << (ostream& os, const map& m){bool isF=true;for(auto& p:m){if(!isF)os< ostream& operator << (ostream& os, const tuple& t){return os << get<0>(t);} template ostream& operator << (ostream& os, const tuple& t){return os << get<0>(t)<<" "<(t);} template ostream& operator << (ostream& os, const tuple& t){return os << get<0>(t)<<" "<(t)<<" "<(t);} template ostream& operator << (ostream& os, const tuple& t){return os << get<0>(t)<<" "<(t)<<" "<(t)<<" "<(t);} template ostream& operator << (ostream& os, const vector& as){for(int i:range(as.size())){if(i!=0)os<<" "; os< ostream& operator << (ostream& os, const vector>& as){for(int i:range(as.size())){if(i!=0)os< inline T INF(){assert(false);}; template<> inline int INF(){return 1<<28;}; template<> inline ll INF(){return 1LL<<60;}; template<> inline double INF(){return 1e16;}; template<> inline long double INF(){return 1e16;}; template inline T EPS(){assert(false);}; template<> inline int EPS(){return 1;}; template<> inline ll EPS(){return 1LL;}; template<> inline double EPS(){return 1e-12;}; template<> inline long double EPS(){return 1e-12;}; // min{2^r | n < 2^r} template inline T upper_pow2(T n){ T res=1;while(res inline T msb(T n){ int d=62;while((1LL<n)d--;return d;} class Main{ public: int N; vector as; vector>> dp; ll dfs(int x,int l,int r){ if(dp[x][l][r] != INF()) return dp[x][l][r]; if(x == 0){ if(l-1 >= 0){ dp[x][l][r] = min(dp[x][l][r],max(dfs(x,l-1,r),as[l-1])+1); } if(r+1 <= N){ dp[x][l][r] = min(dp[x][l][r],max(dfs(1-x,l,r+1),as[r])+(r-l)); } }else{ if(l-1 >= 0){ dp[x][l][r] = min(dp[x][l][r],max(dfs(1-x,l-1,r),as[l-1])+(r-l)); } if(r+1 <= N){ dp[x][l][r] = min(dp[x][l][r],max(dfs(x,l,r+1),as[r])+1); } } return dp[x][l][r]; } void run(){ cin >> N; as = vector(N);cin >> as; dp =vector>>(2,vector>(N,vector(N+1,INF()))); dp[0][0][N] = 0; dp[1][0][N] = 0; ll res = INF(); for(int x:range(2))for(int l:range(N)){ res = min(res,max(dfs(x,l,l+1),as[l])); } cout << res << endl; } }; int main(){ cout <