Solving USACO Name That Number problem in c++

It is always afraid me to recieve file input 

but it is nothing difficult

#include<fstream>
#include <string>
using namespace std;
string memo[13];
int main() {

	string N;
	ifstream openfile("dict.txt");
	ofstream fout("namenum.out");
	ifstream fin("namenum.in");
	bool check = true;
	fin >> N;
	if (openfile.is_open()) {
		string line;
		while (getline(openfile, line)) {
		string answer;
			for (int i = 0; i < line.size(); i++) {
				if (line[i] == 'A' || line[i] == 'B' || line[i] == 'C') {
					answer += "2";
				}
				else if (line[i] == 'D' || line[i] == 'E' || line[i] == 'F') {
					answer += "3";
				}
				else if (line[i] == 'G' || line[i] == 'H' || line[i] == 'I') {
					answer += "4";
				}
				else if (line[i] == 'J' || line[i] == 'K' || line[i] == 'L') {
					answer += "5";
				}
				else if (line[i] == 'M' || line[i] == 'N' || line[i] == 'O') {
					answer += "6";
				}
				else if (line[i] == 'P' || line[i] == 'R' || line[i] == 'S') {
					answer += "7";
				}
				else if (line[i] == 'T' || line[i] == 'U' || line[i] == 'V') {
					answer += "8";
				}
				else if (line[i] == 'W' || line[i] == 'X' || line[i] == 'Y') {
					answer += "9";
				}
			}
			if (answer == N) {
				fout << line<<endl;
				check = false;
			}
		}
	}
	if(check)
		fout << "NONE" << endl;
	return 0;
}