Unable to determine cause due to differences in output

entering
20 2 5

output
84
*Among integers of 20 or less, 2, 3, 4, 5, 11, 12, 13, 14, 20 have the sum of 2 or more digits and 5 or less.Outputs a total of 84 of these.

#include<bits/stdc++.h>

using namespace std;

int log_2(int n, int a, int b){
    
    intans = 0;
    for(inti=1;i<=n;i++){
        int sum = 0;
        int num=i;
        while(num<=0){
            sum+=num%10;
            // cout <<sum <<endl;
            num/=10;
        }
        // cout <<sum <<endl;
        if(a<=sum&&sum<=b){
            an + = i;    
        }
        
    }
    
    returnans;
}


int main() {
    int n, a, b;
    cin>>n>a>b;
    
    cout<<log_2(n,a,b)<<endl;
    
    return 0;
}