RT，满江红

真不知道哪错了

#include<iostream>
#include<string>
#include<map>
using namespace std;
map<string,int> mp;
int cnt;
int main()
{
	int n;
	cin >> n;
	for(int i=1;i<=n;i++)
	{
		int a;
		string b;
		int c;
		cin >> a;
		if(a==1)
		{
			cin>>b>>c;
			if(!mp[b]) cnt++;
			mp[b]=c;
			cout<<"OK\n";
		}
		if(a==2)
		{
			cin >> b;
			if(mp[b]) cout<<mp[b]<<'\n';
			else cout<<"Not found\n";
		}
		if(a==3)
		{
			cin >> b;
			if(mp[b])
			{
				cnt--;
				mp[b]=0;
				cout<<"Deleted successfully\n";
			}
			else cout<<"Not found\n";
		}
		if(a==4) cout << cnt;
	}
	return 0;
}

求dalao指教