How to use if ... else statement with two possibilities in c++?

I have to code a function that validates a text file. I am struggling with the two possibilities.

The first line is always a country. I have created a vector of strings with some country’ names. Then, the second line has to be a city. After, a first and last name follow. However, if the text file contains more information, I have to validate whether the next line is a city or a first name. I thought about incrementing the loop:

Below is my pseudo-code.

while(« reading line by line »){

 i++;

 If line is empty
  Return false
  Else if line is not empty
  Read line;
  i=0;


 if (i%2==1){
 « If line is not city »
     return false;
    else
     Read line;
      i=0;

     else
      If line is empty
      Return false
      Else 
      if line is not empty
      Read line

     if (i%2==0){
     If line is empty
     Return false
     If line is not empty
     Read line}

Then, the program has to start again. However, when I try my program: if I erase the country, the program is still working and skipping the false condition. What should I do?

Thank you