char*->int

int atoi(char*str1) {
	int count = 0;
	int answered=0;
	while (1) {
		if (*(str1 + count) == '\0') {
			break;
		}
		int answer;
		answer = (*(str1 + count)) - 48;
		count++;
		answered = answered *10+answer;
	}

	return answered;
}
int main() {

	char *str1 = (char *)"1234567890";
	int answer=atoi(str1);
	cout << answer;
	return 0;
}