Language: C++

                            #include <bits/stdc++.h>
                            #include<iostream>
                            #include<cstdio>
                            #include<vector>
                            #include<queue>
                            #include<map>
                            #include<cstring>
                            #include<string>
                            #include <math.h>
                            #include<algorithm>
                        //    #include <boost/multiprecision/cpp_int.hpp>
                            #include<functional>
                    #define int long long
                            #define inf  1000000007
                            #define pa pair<int,int>
                            #define ll long long
                            #define pal pair<double,pa>
                            #define ppa pair<int,int>
                            #define ppap pair<int,pa>
                            #define ssa pair<string,int>
                            #define  mp make_pair
                            #define  pb push_back
                            #define EPS (1e-10)
                            #define equals(a,b) (fabs((a)-(b))<EPS)
                     
                            using namespace std;
                  
                            class Point{
                            	public:
                            	double x,y;
                            	Point(double x=0,double y=0):x(x),y(y) {}
                            	Point operator + (Point p) {return Point(x+p.x,y+p.y);}
                            	Point operator - (Point p) {return Point(x-p.x,y-p.y);}
                            	Point operator * (double a) {return Point(x*a,y*a);}
                            	Point operator / (double a) {return Point(x/a,y/a);}
                            	double absv() {return sqrt(norm());}
                            	double norm() {return x*x+y*y;}
                            	bool operator < (const Point &p) const{
                            		return x != p.x ? x<p.x: y<p.y;
                            	}
                            	bool operator == (const Point &p) const{
                            		return fabs(x-p.x)<EPS && fabs(y-p.y)<EPS;
                            	}
                            };
                            typedef Point Vector;
                     
                            struct Segment{
                            Point p1,p2;
                            };
                             double dot(Vector a,Vector b){
                            	return a.x*b.x+a.y*b.y;
                            }
                            double cross(Vector a,Vector b){
                            	return a.x*b.y-a.y*b.x;
                            }
                        
bool parareru(Point a,Point b,Point c,Point d){
//	if(abs(cross(a-b,d-c))<EPS)cout<<"dd "<<cross(a-b,d-c)<<endl;
	return abs(cross(a-b,d-c))<EPS;
}
double distance_ls_p(Point a, Point b, Point c) {
  if ( dot(b-a, c-a) < EPS ) return (c-a).absv();
  if ( dot(a-b, c-b) < EPS ) return (c-b).absv();
  return abs(cross(b-a, c-a)) / (b-a).absv();
}
bool is_intersected_ls(Segment a,Segment b) {
	if(a.p1==b.p1||a.p2==b.p1||a.p1==b.p2||a.p2==b.p2) return false;
	if(parareru((a.p2),(a.p1),(a.p1),(b.p2))&&parareru((a.p2),(a.p1),(a.p1),(b.p1))){
//		cout<<"sss"<<endl;
		if(dot(a.p1-b.p1,a.p1-b.p2)<EPS) return true;
		if(dot(a.p2-b.p1,a.p2-b.p2)<EPS) return true;
		if(dot(a.p1-b.p1,a.p2-b.p1)<EPS) return true;
		if(dot(a.p1-b.p2,a.p2-b.p2)<EPS) return true;
		return false;
	}
  else return ( cross(a.p2-a.p1, b.p1-a.p1) * cross(a.p2-a.p1, b.p2-a.p1) < EPS ) && ( cross(b.p2-b.p1, a.p1-b.p1) * cross(b.p2-b.p1, a.p2-b.p1) < EPS );
}

double segment_dis(Segment a,Segment b){
	if(is_intersected_ls(a,b))return 0;
	double r=distance_ls_p(a.p1, a.p2, b.p1);
	r=min(r,distance_ls_p(a.p1, a.p2, b.p2));
	r=min(r,distance_ls_p(b.p1, b.p2, a.p2));
	r=min(r,distance_ls_p(b.p1, b.p2, a.p1));
	return r;
}
Point intersection_ls(Segment a, Segment b) {
  Point ba = b.p2-b.p1;
  double d1 = abs(cross(ba, a.p1-b.p1));
  double d2 = abs(cross(ba, a.p2-b.p1));
  double t = d1 / (d1 + d2);

  return a.p1 + (a.p2-a.p1) * t;
}

                string itos( int i ) {
                ostringstream s ;
                s << i ;
                return s.str() ;
                }
                 
                int gcd(int v,int b){
                	if(v>b) return gcd(b,v);
                	if(v==b) return b;
                	if(b%v==0) return v;
                	return gcd(v,b%v);
                }
 
                double distans(double x1,double y1,double x2,double y2){
                	double rr=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
                	return sqrt(rr);
                	
                }
                /*
int pr[100010];
//int inv[100010];
*/ 
int beki(int wa,int rr,int warukazu){
	if(rr==0) return 1ll;
	if(rr==1) return wa%warukazu;
	if(rr%2==1) return (beki(wa,rr-1,warukazu)*wa)%warukazu;
	int zx=beki(wa,rr/2,warukazu);
	return (zx*zx)%warukazu;
}
  /*
void gya(){
	pr[0]=1;
	for(int i=1;i<100010;i++){
		pr[i]=(pr[i-1]*i)%inf;
	}
	for(int i=0;i<100010;i++) inv[i]=beki(pr[i],inf-2);
	
}

*/

                         //----------------kokomade tenpure------------


signed main(){
int n;
	cin>>n;
int z[100020];
	for(int i=1;i<=n;i++) cin>>z[i];
	
	vector<int> ve;
	for(int i=1;i<=n;i++)if(z[i]==i) ve.pb(i);
	
	if(ve.size()==0) cout<<0<<endl;
	else if(ve.size()%2==0){
		
		int d=0,dd=2;
		for(int i=0;i<ve.size();i+=2) d+= ve[i+1]-ve[i];
		for(int i=1;i<ve.size()-1;i+=2) dd+= ve[i+1]-ve[i];
		cout<<min(min(ve.size(),d),dd)<<endl;
	}
	else{
		int d=1,dd=1;
		for(int i=0;i<ve.size()-1;i+=2) d+= ve[i+1]-ve[i];
		for(int i=1;i<ve.size();i+=2) dd+= ve[i+1]-ve[i];
		cout<<<min(min(ve.size(),d),dd)<<endl;
	}
	
	return 0;
}



Compiler output:
a.cc: In function 'int main()':
a.cc:155:30: error: no matching function for call to 'min(std::vector<long long int>::size_type, long long int&)'
  155 |                 cout<<min(min(ve.size(),d),dd)<<endl;
      |                           ~~~^~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:233:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::min(const _Tp&, const _Tp&)'
  233 |     min(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note:   template argument deduction/substitution failed:
a.cc:155:30: note:   deduced conflicting types for parameter 'const _Tp' ('long unsigned int' and 'long long int')
  155 |                 cout<<min(min(ve.size(),d),dd)<<endl;
      |                           ~~~^~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::min(const _Tp&, const _Tp&, _Compare)'
  281 |     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5686:5: note: candidate: 'template<class _Tp> constexpr _Tp std::min(initializer_list<_Tp>)'
 5686 |     min(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5686:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5696:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::min(initializer_list<_Tp>, _Compare)'
 5696 |     min(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5696:5: note:   template argument deduction/substitution failed:
a.cc:155:30: note:   mismatched types 'std::initializer_list<_Tp>' and 'long unsigned int'
  155 |                 cout<<min(min(ve.size(),d),dd)<<endl;
      |                           ~~~^~~~~~~~~~~~~
a.cc:161:23: error: expected primary-expression before '<' token
  161 |                 cout<<<min(min(ve.size(),d),dd)<<endl;
      |                       ^
a.cc:161:31: error: no matching function for call to 'min(std::vector<long long int>::size_type, long long int&)'
  161 |                 cout<<<min(min(ve.size(),d),dd)<<endl;
      |                            ~~~^~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::min(const _Tp&, const _Tp&)'
  233 |     min(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note:   template argument deduction/substitution failed:
a.cc:161:31: note:   deduced conflicting types for parameter 'const _Tp' ('long unsigned int' and 'long long int')
  161 |                 cout<<<min(min(ve.size(),d),dd)<<endl;
      |                            ~~~^~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::min(const _Tp&, const _Tp&, _Compare)'
  281 |     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note:   candidate expects 3 arguments, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5686:5: note: candidate: 'template<class _Tp> constexpr _Tp std::min(initializer_list<_Tp>)'
 5686 |     min(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5686:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5696:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::min(initializer_list<_Tp>, _Compare)'
 5696 |     min(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5696:5: note:   template argument deduction/substitution failed:
a.cc:161:31: note:   mismatched types 'std::initializer_list<_Tp>' and 'long unsigned int'
  161 |                 cout<<<min(min(ve.size(),d),dd)<<endl;
      |                            ~~~^~~~~~~~~~~~~