[ybtoj advanced training guidance] judgment overflow [error]

Ideas ：

Because it will exceed the boundary , Then transfer the form of multiplication to the form of division
（ I originally wanted to practice with this problem c++ String input , The result didn't come out ）

$code(wrong)$

#include<iostream>
#include<cstdio>

using namespace std;

int t;

int main()
{
    
	scanf("%d ", &t);
	while(t--)
	{
    
		unsigned long long i;
		string s="", ss="", s1="";
		getline(cin, s1);
		for(i=0; ; i++)
		{
    	
			s=s+s1[i];
			if(s=="int8"||
			s=="unsigned int8"||
			s=="int16"||
			s=="unsigned int16"||
			s=="int32"||
			s=="unsigned int32"||
			s=="int64"||
			s=="unsigned int64")
				break;
		}
		i+=2;
		for(; i<s1.size(); i++)
			ss=ss+s1[i];
		unsigned long long maxx;
		if(s=="int8")
			maxx=127;
		if(s=="unsigned int8")
			maxx=255;
		if(s=="int16")
			maxx=32767;
		if(s=="unsigned int16")
			maxx=65535;
		if(s=="int32")
			maxx=2147483647;
		if(s=="unsigned int32")
			maxx=4294967295;
		if(s=="int64")
			maxx=9223372036854775807;
		if(s=="unsigned int64")
			maxx=18446744073709551615;
		i=0;
		unsigned long long sum=1, flag=1, j=0;
		while(j<ss.size())
		{
    
			unsigned long long b=0;
			for(; j<ss.size()&&ss[j]!=' '; j++)
				b=b*10+ss[j]-48;
			unsigned long long last=sum;
			sum*=b;
			i++;
			if(sum>maxx||sum<0||sum/b!=last)
			{
    
				flag=0;
				break;
			}
			j++;
		}
		if(flag==1)
			printf("never\n");
		else printf("%d\n", i);
	}
	return 0;
}