Language: C++

##python
n = input()
a = int(n[0])
b = int(n[1])
c = int(n[2])
d = int(n[3])

if a+b+c+d == 7:
	print(a, end='')
	print('+', end='')
	print(b, end='')
	print('+', end='')
	print(c, end='')
	print('+', end='')
	print(d, end='')
	print('=7')
    
elif a+b+c-d == 7:
	print(a, end='')
	print('+', end='')
	print(b, end='')
	print('+', end='')
	print(c, end='')
	print('-', end='')
	print(d, end='')
	print('=7')
    
elif a+b-c+d == 7:
	print(a, end='')
	print('+', end='')
	print(b, end='')
	print('-', end='')
	print(c, end='')
	print('+', end='')
	print(d, end='')
	print('=7')
    
elif a-b+c+d == 7:
	print(a, end='')
	print('-', end='')
	print(b, end='')
	print('+', end='')
	print(c, end='')
	print('+', end='')
	print(d, end='')
	print('=7')
    
elif a+b-c-d == 7:
	print(a, end='')
	print('+', end='')
	print(b, end='')
	print('-', end='')
	print(c, end='')
	print('-', end='')
	print(d, end='')
	print('=7')
    
elif a-b-c+d == 7:
	print(a, end='')
	print('-', end='')
	print(b, end='')
	print('-', end='')
	print(c, end='')
	print('+', end='')
	print(d, end='')
	print('=7')
    
elif a-b+c-d == 7:
	print(a, end='')
	print('-', end='')
	print(b, end='')
	print('+', end='')
	print(c, end='')
	print('-', end='')
	print(d, end='')
	print('=7')
    
elif a-b-c-d == 7:
	print(a, end='')
	print('-', end='')
	print(b, end='')
	print('-', end='')
	print(c, end='')
	print('-', end='')
	print(d, end='')
	print('=7')

Compiler output:
a.cc:1:1: error: stray '##' in program
    1 | ##python
      | ^~
a.cc:9:22: error: empty character constant
    9 |         print(a, end='')
      |                      ^~
a.cc:10:24: error: empty character constant
   10 |         print('+', end='')
      |                        ^~
a.cc:11:22: error: empty character constant
   11 |         print(b, end='')
      |                      ^~
a.cc:12:24: error: empty character constant
   12 |         print('+', end='')
      |                        ^~
a.cc:13:22: error: empty character constant
   13 |         print(c, end='')
      |                      ^~
a.cc:14:24: error: empty character constant
   14 |         print('+', end='')
      |                        ^~
a.cc:15:22: error: empty character constant
   15 |         print(d, end='')
      |                      ^~
a.cc:16:15: warning: multi-character character constant [-Wmultichar]
   16 |         print('=7')
      |               ^~~~
a.cc:19:22: error: empty character constant
   19 |         print(a, end='')
      |                      ^~
a.cc:20:24: error: empty character constant
   20 |         print('+', end='')
      |                        ^~
a.cc:21:22: error: empty character constant
   21 |         print(b, end='')
      |                      ^~
a.cc:22:24: error: empty character constant
   22 |         print('+', end='')
      |                        ^~
a.cc:23:22: error: empty character constant
   23 |         print(c, end='')
      |                      ^~
a.cc:24:24: error: empty character constant
   24 |         print('-', end='')
      |                        ^~
a.cc:25:22: error: empty character constant
   25 |         print(d, end='')
      |                      ^~
a.cc:26:15: warning: multi-character character constant [-Wmultichar]
   26 |         print('=7')
      |               ^~~~
a.cc:29:22: error: empty character constant
   29 |         print(a, end='')
      |                      ^~
a.cc:30:24: error: empty character constant
   30 |         print('+', end='')
      |                        ^~
a.cc:31:22: error: empty character constant
   31 |         print(b, end='')
      |                      ^~
a.cc:32:24: error: empty character constant
   32 |         print('-', end='')
      |                        ^~
a.cc:33:22: error: empty character constant
   33 |         print(c, end='')
      |                      ^~
a.cc:34:24: error: empty character constant
   34 |         print('+', end='')
      |                        ^~
a.cc:35:22: error: empty character constant
   35 |         print(d, end='')
      |                      ^~
a.cc:36:15: warning: multi-character character constant [-Wmultichar]
   36 |         print('=7')
      |               ^~~~
a.cc:39:22: error: empty character constant
   39 |         print(a, end='')
      |                      ^~
a.cc:40:24: error: empty character constant
   40 |         print('-', end='')
      |                        ^~
a.cc:41:22: error: empty character constant
   41 |         print(b, end='')
      |                      ^~
a.cc:42:24: error: empty character constant
   42 |         print('+', end='')
      |                        ^~
a.cc:43:22: error: empty character constant
   43 |         print(c, end='')
      |                      ^~
a.cc:44:24: error: empty character constant
   44 |         print('+', end='')
      |                        ^~
a.cc:45:22: error: empty character constant
   45 |         print(d, end='')
      |                      ^~
a.cc:46:15: warning: multi-character character constant [-Wmultichar]
   46 |         print('=7')
      |               ^~~~
a.cc:49:22: error: empty character constant
   49 |         print(a, end='')
      |                      ^~
a.cc:50:24: error: empty character constant
   50 |         print('+', end='')
      |                        ^~
a.cc:51:22: error: empty character constant
   51 |         print(b, end='')
      |                      ^~
a.cc:52:24: error: empty character constant
   52 |         print('-', end='')
      |                        ^~
a.cc:53:22: error: empty character constant
   53 |         print(c, end='')
      |                      ^~
a.cc:54:24: error: empty character constant
   54 |         print('-', end='')
      |                        ^~
a.cc:55:22: error: empty character constant
   55 |         print(d, end='')
      |                      ^~
a.cc:56:15: warning: multi-character character constant [-Wmultichar]
   56 |         print('=7')
      |               ^~~~
a.cc:59:22: error: empty character constant
   59 |         print(a, end='')
      |                      ^~
a.cc:60:24: error: empty character constant
   60 |         print('-', end='')
      |                        ^~
a.cc:61:22: error: empty character constant
   61 |         print(b, end='')
      |                      ^~
a.cc:62:24: error: empty character constant
   62 |         print('-', end='')
      |                        ^~
a.cc:63:22: error: empty character constant
   63 |         print(c, end='')
      |                      ^~
a.cc:64:24: error: empty character constant
   64 |         print('+', end='')
      |                        ^~
a.cc:65:22: error: empty character constant
   65 |         print(d, end='')
      |                      ^~
a.cc:66:15: warning: multi-character character constant [-Wmultichar]
   66 |         print('=7')
      |               ^~~~
a.cc:69:22: error: empty character constant
   69 |         print(a, end='')
      |                      ^~
a.cc:70:24: error: empty character constant
   70 |         print('-', end='')
      |                        ^~
a.cc:71:22: error: empty character constant
   71 |         print(b, end='')
      |                      ^~
a.cc:72:24: error: empty character constant
   72 |         print('+', end='')
      |                        ^~
a.cc:73:22: error: empty character constant
   73 |         print(c, end='')
      |                      ^~
a.cc:74:24: error: empty character constant
   74 |         print('-', end='')
      |                        ^~
a.cc:75:22: error: empty character constant
   75 |         print(d, end='')
      |                      ^~
a.cc:76:15: warning: multi-character character constant [-Wmultichar]
   76 |         print('=7')
      |               ^~~~
a.cc:79:22: error: empty character constant
   79 |         print(a, end='')
      |                      ^~
a.cc:80:24: error: empty character constant
   80 |         print('-', end='')
      |                        ^~
a.cc:81:22: error: empty character constant
   81 |         print(b, end='')
      |                      ^~
a.cc:82:24: error: empty character constant
   82 |         print('-', end='')
      |                        ^~
a.cc:83:22: error: empty character constant
   83 |         print(c, end='')
      |                      ^~
a.cc:84:24: error: empty character constant
   84 |         print('-', end='')
      |                        ^~
a.cc:85:22: error: empty character constant
   85 |         print(d, end='')
      |                      ^~
a.cc:86:15: warning: multi-character character constant [-Wmultichar]
   86 |         print('=7')
      |               ^~~~
a.cc:1:3: error: 'python' does not name a type
    1 | ##python
      |   ^~~~~~