No of 1's in <=n

#include <iostream>
using namespace std;

int count1(int n){
    
    if(n == 0){
        return 0;
    }
    if(n == 1){
        return 1;
    }
    
    int countof1innm1 = count1(n-1);
    int countinn = 0;
    
    while(n !=0){
        int rem = n%10;
        if(rem ==1){
            countinn++;
        }
        n = n/10;
    }
    
    return countinn + countof1innm1;
    
    
}


int main() {
    
    int n;
    cin>>n;
    cout<<count1(n);
    
}