输入不确定的数字

如何输入不确定的数字。
#include <bits/stdc++.h>
using namespace std;

int b[9] = {
    
    3, 3, 3, 3, 3, 3, 3, 3, 3};
int i;
int main () {
    
    
	string a;
	cin >> a;
	for (int i = 0; i < a.length(); i++) {
    
    
		a[i] = a[i] - '0';//即使相同，也要这样转化成数字。
	}
	for ( i = 0; i < a.length(); i = i + 2) {
    
    
		b[a[i] - 1] = 1;
	}
	for ( i = 1; i < a.length(); i = i + 2) {
    
    
		b[a[i] - 1] = 2;
	}
	if ((b[0] == 1 && b[4] == 1 && b[8] == 1) || (b[2] == 1 && b[4] == 1 && b[6] == 1) || (b[0] == 1 && b[1] == 1
	        && b[2] == 1) || (b[3] == 1 && b[4] == 1 && b[5] == 1) || (b[6] == 1 && b[7] == 1 && b[8] == 1) || (b[0] == 1
	                && b[3] == 1 && b[6] == 1) || (b[1] == 1 && b[4] == 1 && b[7] == 1) || (b[2] == 1 && b[5] == 1 && b[8] == 1))
		cout << "xiaoa" << ' ' << "wins." << endl;
	else if ((b[0] == 2 && b[4] == 2 && b[8] == 2) || (b[2] == 2 && b[4] == 2 && b[6] == 2) || (b[0] == 2 && b[1] == 2
	         && b[2] == 2) || (b[3] == 2 && b[4] == 2 && b[5] == 2) || (b[6] == 2 && b[7] == 2 && b[8] == 2) || (b[0] == 2
	                 && b[3] == 2 && b[6] == 2) || (b[1] == 2 && b[4] == 2 && b[7] == 2) || (b[2] == 2 && b[5] == 2 && b[8] == 2))
		cout << "uim" << ' ' << "wins." << endl;
	else
		cout << "drew." << endl;
	return 0;
}