Código oscuro

#include <stdio.h>
#include <string.h>

int main(void)
{
int a; int b; int c;
char s[] = "Codigo oscuro";

a = 0;
c = strlen(s);
while (a < c){
b = s[i] + 10;
if (b > 122)
b = b - 90 ;
printf("%c", b);
a++;
}
return 0;
}