Line 11: Char 24: error: no member named 'second' in 'std::map<char, int>' 11 | if(mpp.second()==1){ | ~~~ ^

The error message is indicating that you're trying to access a member named 'second' in 'std::map<char, int>', which doesn't exist.

In C++, a map is a container that stores elements formed by a combination of a key value and a mapped value. The 'second' member is not a function of the map itself, but a property of an element in the map.

To access the 'second' member (which refers to the mapped value), you need to first get an iterator to the element. Here's how you can do it:

for(auto it = mpp.begin(); it != mpp.end(); ++it) {
    if(it->second == 1) {
        // do something
    }
}

In this code, 'it' is an iterator that points to the current element in the map. 'it->second' gives you the mapped value of the current element.