Primary school students fun C ++ programming

#include<iostream> 
using namespace std;
int main()
{
  int n,nike,glair,num=0;
  nike=glair=0;
  n=0;
  do
  {
    nike++;
    if(nike>20) nike=1;
    glair++;
    if(glair>30) glair=1;
    if(nike==glair) num++;
    n++;
  }while(n<1000);
  cout<<num;
  return 0;
}