help with strings

[Showdon]

So I'm trying to make a program to pull the last 2 numbers off a 5 digit number and output the corresponding color with the number.The program won't run and comes back with this error located at the bottom.

#include <iostream>
#include <string>

using namespace std;

int main()
{
	string invcode;

	cout<< "Enter the 5 digit inventory code: ";
	cin>>invcode;

    if(invcode.substr(3,2)=41)
    {
        cout<<"Red"<<endl;
    }
    else if(invcode.substr(3,2)=25)
    {
        cout<<"Black"<<endl;
    }
    else if(invcode.substr(3,2)=30)
    {
        cout<<"Green"<<endl;
    }
    else
    {
        cout<<"Invalid inventory code"<<endl;
    }
	system("pause");
	return 0;
}

17|error: could not convert `(&std::basic_string<_CharT, _Traits, _Alloc>::substr(typename _Alloc::size_type, typename _Alloc::size_type) const [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](3u, 2u))->std::basic_string<_CharT, _Traits, _Alloc>::operator= [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](((const char*)"41"))' to `bool'|
C:\Users\Showdon\Desktop\C++\Lab15\Lab1501\main.cpp|21|error: could not convert `(&std::basic_string<_CharT, _Traits, _Alloc>::substr(typename _Alloc::size_type, typename _Alloc::size_type) const [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](3u, 2u))->std::basic_string<_CharT, _Traits, _Alloc>::operator= [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](25)' to `bool'|
C:\Users\Showdon\Desktop\C++\Lab15\Lab1501\main.cpp|25|error: could not convert `(&std::basic_string<_CharT, _Traits, _Alloc>::substr(typename _Alloc::size_type, typename _Alloc::size_type) const [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](3u, 2u))->std::basic_string<_CharT, _Traits, _Alloc>::operator= [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>](30)' to `bool'|
||=== Build finished: 3 errors, 0 warnings ===|

[Peter87]

Use == for comparison. = is for assignment.

You can't compare a string and an integer by using ==. Change the numbers you compare to strings

if(invcode.substr(3,2) == "41")
{
	...

or change invcode to int and use % to get the two last digits

if(invcode % 100 == 41)
{
	...

[Showdon]

Wow duh! Thanks for pointing out the obvious. Totally forgot about the difference of == and =. Thanks