Файловый ввод-вывод

#include <cstdio>

using namespace std;

int main() {
	int a, b;
	FILE *fin, *fout;
	fin = fopen("sum.in", "r");
	fout = fopen("sum.out", "w");
	fscanf(fin, "%d%d", &a, &b);
	fprintf(fout, "%d\n", a + b);
	fclose(fin);
	fclose(fout);
	return 0;
}

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#include <fstream>

using namespace std;

int main() {
	int a, b;
	ifstream fin("sum.in");
	ofstream fout("sum.out");
	fin >> a >> b;
	fout << a + b << endl;
	fin.close();
	fout.close();
	return 0;
}

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#include <iostream>
#include <cstdio>

using namespace std;

int main() {
	int a, b;
	freopen("sum.in", "r", stdin);
	freopen("sum.out", "w", stdout);
	cin >> a >> b;
	cout << a + b << endl;
	fclose(stdin);
	fclose(stdout);
	return 0;
}

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#include <iostream>

#include <cstdio>

using namespace std;

int main() {
	int a, b;
	freopen("sum.in", "r", stdin);
	freopen("sum.out", "w", stdout);
	scanf("%d%d", &a, &b);
	printf("%d\n", a + b);
	fclose(stdin);
	fclose(stdout);
	return 0;
}