subtract.cpp

#include<bits/stdc++.h>
using namespace std;






string add (string num1, string num2)
{

int l1 = num1.length() - 1;
int l2 = num2.length() - 1;

if(l1 <= l2)
{ 
	for(int i=l2; i>=l2-l1; i--)
	num1[i] = num1[i-l2+l1];

	
	for(int j=l2-l1-1; j>=0; j--)
    num1[j] = '0';
	
    l1 = l2;
    num1[l1+1] = '\0';
}

else
{
	for(int i=l1; i>=l1-l2; i--)
	num2[i] = num2[i-l1+l2];

	for(int j=l1-l2-1; j>=0; j--)
    num2[j] = '0';

    l2 = l1;
    num2[l2+1] = '\0';
}


string sum = "\0";
int rem = 0;

for(int k=0; k<=l2; k++)
{
	sum[k] = num1[l2-k] - 48 + num2[l2-k] - 48 + rem + 48;

	if(sum[k]>=58)
	{sum[k] -= 10;
	 rem = 1;}

	 else
	 rem = 0;


	sum += sum[k];

}
if(rem==1)
{sum += rem + 48;
sum[l1+2] = '\0';}

else
sum[l1+1] = '\0';

reverse(sum.begin(),sum.end());
return sum;
}






string comp(string num2)
{
	int l2 = num2.length() - 1;
	string num3 = num2;
int i = l2;

while(num2[i]=='0')
{   
	i--;
}

num2[i] = 106 - num2[i];
i--;

for(; i>=0; i--)
{
	num2[i] = 105 - num2[i];
}
  return num2;
}







int main() {

string num1, num2;
cin >> num1;
cin >> num2;

int l1 = num1.length() - 1, l2 = num2.length() - 1;
string num3 = num2;
num2 = comp(num2);

string num4 = add(num1, num2);

int l4 = num4.length() - 1;

if(l4 > l2)
{ 
	num4[0] -= 1;
}

else 
{
	num4 = "-" + comp(num4);
}

cout << num4 << endl;

	return 0;
}