text: #include<bits/stdc++.h>
  using namespace std;
  
  int main(){
      int start=0,mid=0,end=5;
      int arr[]={0,3,2,7,4,1};
      while(mid<=end){
          if(arr[mid]==0){
              swap(arr[start++],arr[mid++]);
              cout<<mid;
              break;
          }
  
      }
      return 0;
  }