Else if statement not functioning properly

I was solving the balanced parentheses problem using stack implementation when I came across this situation wherein I was using the 'else-if' statements to check for the closing braces but this gave a different output than the expected one. On changing all the 'else-if' statements to plain 'if' statements the code worked just fine. I want to know why this happened because I always thought that using 'else-if' statements was a better practice.

int main(){
    stack<char> bracks;
    string s;   // input string: {a+(b+c-[e-f])*d}
    cin >> s;
    for(int i = 0; i < s.size(); i++){
        if(s[i] == '{' || s[i] == '(' || s[i] == '[')    bracks.push(s[i]);
        else if(s[i] == '}')
            if(bracks.top() == '{')    bracks.pop();
        else if(s[i] == ')')
            if(bracks.top() == '(')    bracks.pop();
        else if(s[i] == ']')
            if(bracks.top() == '[')    bracks.pop();
    }
    if(bracks.empty())  cout << "Balanced\n";
    else    cout << "Unbalanced\n";
}

Expected output for the input string : "{a+(b+c-[e-f])*d}" is "Balanced" but I'm getting "Unbalanced" as the output.