首先要注意score的范围，所以要用long long int，其次OK两个字母都是大写，并且插入和修改后都要输出Ok
#include<iostream>
#include<set>
#include<map>
#define int long long
using namespace std;
signed main() {map<string, int>mapstudent;int n;cin >> n;while (n--) {int op;cin >> op;if (op == 1) {int score;string name;cin >> name >> score;auto it=mapstudent.find(name);if (it == mapstudent.end())mapstudent.insert(pair<string, int>(name, score)), cout << "OK" << endl;else it->second = score,cout<<"OK"<<endl;}if (op == 2) {string name;cin >> name;auto it = mapstudent.find(name);if (it == mapstudent.end())cout << "Not found" << endl;else cout << it->second << endl;}if (op == 3) {string name;cin >> name;auto it = mapstudent.find(name);if (it == mapstudent.end())cout << "Not found" << endl;else {mapstudent.erase(it);cout << "Deleted successfully" << endl;}}if (op == 4)cout << mapstudent.size() << endl;}return 0;
}
