#include <stdio.h> 
#include <stdlib.h>
#include <string.h>
//checkmailaddress.c

//----------------------------------------
// Function to check the character 
// is an alphabet or not 
int isChar(char c) 
{ 
    return ((c >= 'a' && c <= 'z') 
	    || (c >= 'A' && c <= 'Z')); 
} 
//-----------------------------------------
// Function to check the character 
// is an digit or not 
int isDigit(const char c) 
{ 
    return (c >= '0' && c <= '9'); 
} 
//-----------------------------------------
// Function to check email id is valid or not 
int is_valid(char* email) 
{ 
    // Check the first character 
    // is an alphabet or not 
    if (!isChar(email[0])) { 

	// If it's not an alphabet 
	// email id is not valid 
	return 0; 
    } 
    // Variable to store position 
    // of At and Dot 
    int At = -1, Dot = -1; 
    int len;
    // Traverse over the email id 
    // string to find position of 
    // Dot and At 
	len = strlen(email);
// check mailadresse ob kleiner als 7 ist
	if (len<7) return 0;
    for (int i = 0; 
	i < len; i++) { 
	// If the character is '@' and the name is longer then 1 char
	if (email[i] == '@' && i > 0) { At = i;	} 
	// If character is '.' and the domain is min 2 chars long
	else if (email[i] == '.' && (len-2) > i ) {   Dot = i;} 
    } 
    //If At and Dot are together with no char between
    if (At+1 == Dot)			return 0;
    // If At or Dot is not present 
    if (At == -1 || Dot == -1) 		return 0; 
    // If Dot is present before At 
    if (At > Dot) 			return 0; 
    // If Dot is present at the end 
    if (Dot >= (len-1))			return 1;
} 

// ################################################# 
int main(int argc, char *argv[]) 
{ 
    if (argc != 2){
    fprintf(stderr,"usage: %s emailaddress\n",argv[0]);
    exit (EXIT_FAILURE);
    }
    // Given string email 
    char* email = argv[1]; 

    // Function Call 
    int ans = is_valid(email); 

    // Print the result 
    if (ans) {  printf("%s : valid\n",email);  } 
    else {      printf("%s : invalid\n",email);} 

    return (EXIT_SUCCESS); 
}