Language: C++

#include <algorithm>
#include <bitset>
#include <tuple>
#include <cstdint>
#include <cstdio>
#include <cctype>
#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <limits>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
//using ll=long long;
#define int long long
#define _CRT_SECURE_NO_WARNINGS
#define rep(i, n) for (int i = 0; i < n; i++)
#define _GLIBCXX_DEBUG
const int MOD = 1e9 + 7;
const int INF = 1e18 + 9;
constexpr long double pi = 3.141592653589793238462643383279; //円周率
/*---------------------便利な関数--------------------------------------*/
int fact(int i) {       //階乗
    if (i == 0) return 1;
    return (fact(i - 1)) * i;
}
 
int gcd(int a, int b) {        //最大公約数
    if (b == 0) return a;
    return gcd(b, a % b);
}
 
int lcm(int a, int b) {      //最小公倍数
    return a * b / gcd(a, b);
}
 
int keta(int n) {        //桁数を求める
    if (n == 0) return 1;
    int count = 0;
    while (n != 0) {
        n /= 10;
        count++;
    }
    return count;
}
 
int ketasum(int n) {    //各桁の和
    int sum = 0;
    while (n != 0) {
        sum += n % 10;
        n /= 10;
    }
    return sum;
}
//最小化問題(DP)
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
//最大化問題(DP)
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

//dp注意点
//問題の種類	 初期化する値	 備考
//最小化問題 	INF	
//最大化問題	    -INF	 テーブル全体で 00 以上の値しかとらないことがわかっていれば −1−1 でもいいですし、00 でもいい場合もあります
//数え上げ問題	00	
//確率問題	      00	
//Yes/No 判定問題	False
/*-------------ここまで---------------------------------------------*/
 
signed main(void){
  int x;
  cin>>x;
  if(x>=400 && x<600) cout<<"8"<<endl;
  else if(x>600 && x<800) cout<"7"<<endl;
  else if(x>800 && x<1000) cout<"6"<<endl;
  else if(x>1000 && x<1200) cout<"5"<<endl;
  else if(x>1200 && x<1400) cout<"4"<<endl;
  else if(x>1400 && x<1600) cout<"3"<<endl;
  else if(x>1600 && x<1800) cout<"2"<<endl;
  else if(x>1800 && x<2000) cout<"1"<<endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:107:35: error: invalid operands of types 'const char [2]' and '<unresolved overloaded function type>' to binary 'operator<<'
  107 |   else if(x>600 && x<800) cout<"7"<<endl;
      |                                ~~~^~~~~~
a.cc:108:36: error: invalid operands of types 'const char [2]' and '<unresolved overloaded function type>' to binary 'operator<<'
  108 |   else if(x>800 && x<1000) cout<"6"<<endl;
      |                                 ~~~^~~~~~
a.cc:109:37: error: invalid operands of types 'const char [2]' and '<unresolved overloaded function type>' to binary 'operator<<'
  109 |   else if(x>1000 && x<1200) cout<"5"<<endl;
      |                                  ~~~^~~~~~
a.cc:110:37: error: invalid operands of types 'const char [2]' and '<unresolved overloaded function type>' to binary 'operator<<'
  110 |   else if(x>1200 && x<1400) cout<"4"<<endl;
      |                                  ~~~^~~~~~
a.cc:111:37: error: invalid operands of types 'const char [2]' and '<unresolved overloaded function type>' to binary 'operator<<'
  111 |   else if(x>1400 && x<1600) cout<"3"<<endl;
      |                                  ~~~^~~~~~
a.cc:112:37: error: invalid operands of types 'const char [2]' and '<unresolved overloaded function type>' to binary 'operator<<'
  112 |   else if(x>1600 && x<1800) cout<"2"<<endl;
      |                                  ~~~^~~~~~
a.cc:113:37: error: invalid operands of types 'const char [2]' and '<unresolved overloaded function type>' to binary 'operator<<'
  113 |   else if(x>1800 && x<2000) cout<"1"<<endl;
      |                                  ~~~^~~~~~