#include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

#define N 200

//反转字符串
string res(string s)
{
	int i = 0;
	int j = s.length() - 1;

	while (i < j)
	{
		swap(s[i], s[j]);
		i++;
		j--;
	}

	return s;
}

//转换字符串为int数组
int pub(string s1, string s2, int a[], int b[])
{
	s1 = res(s1);
	s2 = res(s2);

	int len1 = s1.length();
	int len2 = s2.length();
	int i, maxlen;
	maxlen = (len1 > len2) ? len1 : len2;

	for (i = 0; i < len1; i++)
	{
		a[i] = s1[i] - '0';
	}

	for (i = 0; i < len2; i++)
	{
		b[i] = s2[i] - '0';
	}

	return maxlen;
}

//加法运算
void add(string s1, string s2)
{
	int a[N] = {0}, b[N] = {0}, c[N] = {0};
	int i, maxlen;
	maxlen = pub(s1, s2, a, b);

	for (i = 0; i < maxlen; i++)
	{
		c[i] = a[i] + b[i];
	}

	for (i = 0; i < maxlen; i++)
	{
		if (c[i] >= 10)
		{
			c[i] = c[i] - 10;
			c[i + 1]++;

			if (maxlen - 1 == i)
			{
				maxlen++;
			}
		}
	}

	for (i = maxlen - 1; i >= 0; i--)
	{
		cout << c[i];
	}

	cout << endl;
}

//减法运算
void sub(string s1, string s2)
{
	int a[N] = {0}, b[N] = {0}, c[N] = {0};
	int i, maxlen, resultlen = -1;
	bool aSmall = false;

	//两数相等直接输出0
	if (s1.compare(s2) == 0)
	{
		cout << 0 << endl;
		return;
	}

	int len1 = s1.length();
	int len2 = s2.length();

	if (len1 == len2)
	{
		aSmall = s1 < s2;
	}
	else
	{
		aSmall = len1 < len2;
	}

	maxlen = pub(s1, s2, a, b);

	if (aSmall)
	{
		cout << '-';

		for (i = 0; i < maxlen; i++)
		{
			c[i] = b[i] - a[i];
		}
	}
	else
	{
		for (i = 0; i < maxlen; i++)
		{
			c[i] = a[i] - b[i];
		}
	}

	for (i = 0; i < maxlen; i++)
	{
		if (c[i] < 0)
		{
			c[i] = c[i] + 10;
			c[i + 1]--;

			if (maxlen - 1 == i)
			{
				maxlen++;
			}
		}
	}
	/////////////////////////
	//去掉结果前的0
	for (i = maxlen; i > 0; i--)
	{
		if (c[i] != 0)
			break;
		else if (c[i] == 0)
		{
			resultlen = i - 1;
		}
	}

	if (resultlen > 0)
	{
		maxlen = resultlen;
	}
	else
	{
		maxlen = 0;
	}

	////////////////////////

	for (i = maxlen; i >= 0; i--)
	{
		cout << c[i];
	}

	cout << endl;
}

int main()
{
	string s1, s2;
	char ch;
	do
	{
		cout << "输入2个正整数：\n";
		cin >> s1 >> s2;
		if (!isdigit(s1[0]) || !isdigit(s2[0]))
			break;
		cout << "\n输入操作符（+或者-）：";
		cin >> ch;

		switch (ch)
		{
		case '+':
			add(s1, s2);
			break;

		case '-':
			sub(s1, s2);
			break;
		}
		cout << endl;
	} while (true);

	system("pause");
	return 0;
}