text: #include <stdio.h>
  
  #define MAXLINE 1000
  
  int any(char s1[], char s2[]);
  
  int main(int argc, char** argv) {
  
      char s1[MAXLINE] = "This is a test.";
      char s_ok[] = "b.ac";
      char s_ko[] = "yxz";
      char s_empty[] = "";
      int pos;
  
      pos = any(s1, s_ok);
      if (pos == -1)
          printf("Nothing found\n");
      else
          printf("Found at position %d\n", pos);
  
      pos = any(s1, s_ko);
      if (pos == -1)
          printf("Nothing found\n");
      else
          printf("Found at position %d\n", pos);
  
      pos = any(s1, s_empty);
      if (pos == -1)
          printf("Nothing found\n");
      else
          printf("Found at position %d\n", pos);
  
      return 0;
  }
  
  int any(char s1[], char s2[]) {
  
      int i, j;
  
      for (i = 0; s1[i] != '\0'; i++)
          for (j = 0; s2[j] != '\0'; j++)
              if (s1[i] == s2[j])
                  return i;
  
      return -1;
  }
  