#include <iostream>


using namespace std;

int my_strlen(char *str) {
    int n = 0;
    while (str[n] != '\0')
        n++;
    return n;
}

void my_strcpy(char *source, char *target) {
    int i = 0;
    while ((source[i] = target[i]) != '\0')
        i++;
    source[i] = target[i];
}

int my_strstr(char *haystack, char *needle) {
    int k, count = 0, len, c = 0;
    len = my_strlen(needle);
    for (int i = 0; haystack[i] != '\0'; i++) {
        c++;
        k = i;
        for (int j = 0; needle[j] != '\0'; j++) {
            if (haystack[k] != needle[j])
                break;
            count++;
            k++;
        }
        if (count == len)
            return i + 1;
        count = 0;
    }
    return -1;
}

int main() {
    char a[] = "";
    int method;
    cout << "Enter the desired function (strlen - 1, strcpy - 2, strstr - 3)" << endl;
    cin >> method;
    if (method == 1) {
        int kol = my_strlen(a);
        cout << kol;
    }

    if (method == 2) {
        char b[] = "";
        my_strcpy(a, b);
        for (int i = 0; i < my_strlen(a); i++){
            cout << a[i];
        }
    }
    if (method == 3) {
        char b[] = "";
        cout << my_strstr(a, b);
    }

}