Konvert Hexa ke Decimal

konvert hexa ke decimal menggunakan visual C atu GCC di linux gak masalah.
#include
#include
#include
int main(){

char hex[20];

int i,n,dec[20],sum=0,p;

printf("Masukkan nilai Hexa : ");

gets(hex);

n=strlen(hex);

for(i=n-1;i>=0;i--){

p=n-i-1;

if(hex[i]>=65 && hex[i] <= 70)hex[i]-=55;

if(hex[i]>=49 && hex[i] <= 57)hex[i]-=48;

if(hex[i]>=97 && hex[i] <= 102)hex[i]-=87;

dec[i]=hex[i]*pow(16,p);

sum+=dec[i];

printf("\n");

}

printf("Hasil konversi = %d\n",sum);

return 0;

}