Traffic jam

input/code.cpp: In function 'int main()':
input/code.cpp:24:5: error: return-statement with no value, in function returning 'int' [-fpermissive]
   24 |     return;
      |     ^~~~~~
input/code.cpp:26:9: error: redeclaration of 'int max'
   26 |     int max = 0;
      |         ^~~
input/code.cpp:18:9: note: 'int max' previously declared here
   18 |     int max = 0;
      |         ^~~
input/code.cpp:29:12: error: 'arr' was not declared in this scope; did you mean 'arr2'?
   29 |         if(arr[i] > max) max = arr[i];
      |            ^~~
      |            arr2
input/code.cpp:30:12: error: 'arr' was not declared in this scope; did you mean 'arr2'?
   30 |         if(arr[i] < min) min = arr[i];
      |            ^~~
      |            arr2
input/code.cpp:37:16: error: 'arr' was not declared in this scope; did you mean 'arr2'?
   37 |             if(arr[2*j] <= i && arr[2*j+1] >= i) {
      |                ^~~
      |                arr2

#include <iostream>

using namespace std;

int main() {
    int n;
    cin >> n;
    //int arr [2*n];
    int arr2 [604800];

    for(int i = 0; i < n; i++) {
        int a,b;
        cin >> a >> b;
        for(int j = a; j <= b; j++) {
            arr2[j]++;
        }
    }
    int max = 0;
    for(int i = 0; i < 604800; i++) {
        if(arr2[i] > max) max = arr2[i];
    }
    cout << arr2[max] << endl;

    return;

    int max = 0;
    int min = 604800;
    for(int i = 0; i < n; i++) {
        if(arr[i] > max) max = arr[i];
        if(arr[i] < min) min = arr[i];
    }

    int maxnumtotal = 0;
    for(int i = min; i < max; i++) {
        int maxNum = 0;
        for(int j = 0; j < n; j++) {
            if(arr[2*j] <= i && arr[2*j+1] >= i) {
                maxNum++;       
            }
        }
        if (maxNum > maxnumtotal) maxnumtotal = maxNum;
        if( maxNum == n) break;
    }
    cout << maxnumtotal << endl;
  
    
}