[PAT Advanced Level]1031. Hello World for U (20)

#include   
#include   
using namespace std;  
  
int main()  
{  
    string s;  
    cin>>s;  
    int n1, n2;  
    n2 = (s.size() % 2 == 1) 3 : 4;  
    while (n2 <= s.size())  
    {  
        n1 = (s.size() - n2)/2 + 1;  
        if(n1 <= n2) break;  
        n2 += 2;  
    }  
    int i = 0;  
    for(; i < n1 - 1; i++)  
    {  
        cout<