62 13 'N' was not declared in this scope

#include <bits/stdc++.h>
using namespace std;
int main()
{
	string str;
	char ch;
	cin >> str;
	str += '/';
	long long str_wei = 0;
	long long dengyu;	
	bool bl = 1;
	while (str[str_wei] != '/')
	{		
		if (str[str_wei] == '=')
			dengyu = str_wei;
		if (str[str_wei] != '-' && str[str_wei] != '+' && str[str_wei] != '=' && !(str[str_wei] >= '0' && str[str_wei] <= '9') && bl)
		{
			bl = 0;
			ch = str[str_wei];
		}
		str_wei++;
	}
	long long N_wei;
	char N_N[21];	
	char zhfu_dengyu, zhfu_zhfu;	
	long long N = 0;
	long long X = 0; 
	for (int i = 0; i < str_wei; i++)
	{
		if (i < dengyu)
			zhfu_dengyu = 1;
		else
			zhfu_dengyu = -1;
		if (str[i] != '-')
			zhfu_dengyu = 1;
		else
			zhfu_dengyu = -1;	
		N_wei = 0;
		while (str[i] >= '0' && str[i] <= '9')
		{
			N_N[N_wei] = str[i] - '0';
			N_wei++;
			i++;
			bl = 1;
		}
		if (bl)
			N_wei--;
			if (str[i] == ch)
			{
				for (long long wei = N_wei; wei >= 0; wei--)
					X += zhfu_dengyu * zhfu_zhfu * N_N[N_wei - wei] * pow(10, wei);
			}
			else
			{
				for (long long wei = N_wei; wei >= 0; wei--)
					N -= zhfu_dengyu * zhfu_zhfu * N_N[N_wei - wei] * pow(10, wei);
			}
			i--;
			bl = 0;
		}
	}
	double d = N / 1.0 / X;
	cout << fixed << setprecision(3) << d << endl;
	return 0;
}