#include<iostream>
using namespace std;
int char_16_to_int(char * str)
{
if (str == NULL)
return 0;
int sum = 0;
while(*str != '\0')
{
if (*str<='9' && *str>='0') sum = sum *16 + int(*str - '0');
if (*str<='F' && *str>='A') sum = sum *16 + int(*str - 'A')+10;
str++;
}
return sum;
}
int main()
{
char str[] ="123";
int a= char_16_to_int(str);
cout<<"a="<<a<<endl;
}