char s[10] = {'F', 'F', 'F', 'F'};
int t = strlen(s);
long sum = 0;
for(int i = 0; i < t; i++) {
if(s >= 'A' && s <= 'Z')[ i]
s = (s - 'A') + 10 + '0';
sum += ((s-'0')*(pow(16,t-1-i)));
}
char b[10];
int index = 0;
while(sum/10>1){
b[index] = sum%10;
index ++;
sum = sum/10;
}
b[index] = sum%10;
index ++;
sum = sum/10;
while(index<10){
b[index] = 15;
index++;
}