How to ignore letter case for if statement inn C++ [duplicate]

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• Case-insensitive string comparison in C++ [closed] 31 answers

I have the following program:

cout << "enter yes if you like pizza" << endl;
string a;
cin >> a;

if ( a == "yes" ) {

cout << "you are cool" << endl;
}

the problem is when the input is for example "Yes" "yAs" ... i have seen solutions for this that are for c# but they don't work for me...