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

#define MAX_ATTEMPTS 3
#define MAX_USERS 5
#define MAX_USERNAME_LENGTH 20
#define MAX_PASSWORD_LENGTH 20

typedef struct {
    char username[MAX_USERNAME_LENGTH];
    char password[MAX_PASSWORD_LENGTH];
} User;

int main() {
    User users[MAX_USERS] = {
        {"user1", "pass1"},
        {"user2", "pass2"},
        {"user3", "pass3"},
        {"user4", "pass4"},
        {"user5", "pass5"}
    };

    int attempts = 0;
    int authenticated = 0;

    while (attempts < MAX_ATTEMPTS && !authenticated) {
        char inputUsername[MAX_USERNAME_LENGTH];
        char inputPassword[MAX_PASSWORD_LENGTH];

        printf("Enter username: ");
        scanf("%s", inputUsername);
        printf("Enter password: ");
        scanf("%s", inputPassword);

        for (int i = 0; i < MAX_USERS; i++) {
            if (strcmp(inputUsername, users[i].username) == 0 && strcmp(inputPassword, users[i].password) == 0) {
                authenticated = 1;
                break;
            }
        }

        if (!authenticated) {
            attempts++;
            printf("Authentication failed, try again.\n");
        }
    }

    if (authenticated) {
        printf("Authentication successful.\n");
    } else {
        printf("Limit exceeded. Exiting.\n");
    }

    return 0;
}