求大佬帮助awa

我是第二次写 但是我不是到错哪了

#include<iostream>
using namespace std;
int arr[1005];
int main(){
	int a;
	long long int_s,c=0;
	char str;
	cin >> a >> str;
	if (str >= 'A' && str <= 'Z'){
        switch(str){
        	case 'A':
        	int_s = 10;
			break;
			case 'B':
        	int_s = 11;
			break;
			case 'C':
        	int_s = 12;
			break;
			case 'D':
        	int_s = 13;
			break;
			case 'E':
        	int_s = 14;
			break;
			case 'F':
        	int_s = 15;
			break;
		}
    }else if (str >='0' && str <='9'){
        int_s = str;
    }
    while (int_s == 0){
    	arr[c] = int_s % a;
    	int_s /= a;
    	c ++;
	}
	for (int i = 0;i <= c;i ++){
		cout << arr[i];
	}
    return 0;
}