Pre-View#4B

#include <string>
#include <stack>
#include <iostream>

int main(){
    //considering input as valid parentheses
    std::string inp;
    std::cin >> inp;
    std::stack<bool> st;
    for(uint64_t idx = 0; idx < inp.size(); idx++){
        if (inp[idx] == '(') st.push(true);
        if ( inp[idx] == ')' && ( st.empty() || !st.top() ) ) { std::cout << "NOT OK"; exit(0);}
        if (inp[idx] == ')' && st.top()) st.pop();
        if (inp[idx] == '{') st.push(false);
        if ( inp[idx] == '}' && ( st.empty() || st.top() ) ) { std::cout << "NOT OK"; exit(0);}
        if (inp[idx] == '}' && !st.top()) st.pop();
    }
    std::cout << (st.empty() ? "OK": "NOT OK");
    return 0;
}