Language: C

#include<stdio.h>
int main(void){
    int a,b,sum;
    int min=99999;
    int box=0;

    //printf("Input the natural number SUM:");
    scanf("%d",&sum);

    int i,j;
    for(a=1;a<sum;a++){
        b=sum-a;
        if(a>=10000){
            box+=a\10000;
            box+=(a\1000)%10;
            box+=(a\100)%10;
            box+=(a\10)%10;
            box+=a%10;
        }
        else if(a>=1000){
            box+=a\1000;
            box+=(a\100)%10;
            box+=(a\10)%10;
            box+=a%10;
        }
        else if(a>=100){
            box+=a\100;
            box+=(a\10)%10;
            box+=a%10;
        }
        else if(a>=10){
            box+=a\10;
            box+=a%10;
        }
        else{
            box+=a%10;
        }
         if(b>=10000){
            box+=b\10000;
            box+=(b\1000)%10;
            box+=(b\100)%10;
            box+=(b\10)%10;
            box+=b%10;
        }
        else if(b>=1000){
            box+=b\1000;
            box+=(b\100)%10;
            box+=(b\10)%10;
            box+=b%10;
        }
        else if(b>=100){
            box+=b\100;
            box+=(b\10)%10;
            box+=b%10;
        }
        else if(b>=10){
            box+=b\10;
            box+=b%10;
        }
        else{
            box+=b%10;
        }

        if(box<min){
            min=box;
        }
    }
    printf("%d",min);

   
}

Compiler output:
main.c: In function 'main':
main.c:14:19: error: stray '\' in program
   14 |             box+=a\10000;
      |                   ^
main.c:14:19: error: expected ';' before numeric constant
   14 |             box+=a\10000;
      |                   ^~~~~~
      |                   ;
main.c:15:20: error: stray '\' in program
   15 |             box+=(a\1000)%10;
      |                    ^
main.c:15:20: error: expected ')' before numeric constant
   15 |             box+=(a\1000)%10;
      |                  ~ ^~~~~
      |                    )
main.c:16:20: error: stray '\' in program
   16 |             box+=(a\100)%10;
      |                    ^
main.c:16:20: error: expected ')' before numeric constant
   16 |             box+=(a\100)%10;
      |                  ~ ^~~~
      |                    )
main.c:17:20: error: stray '\' in program
   17 |             box+=(a\10)%10;
      |                    ^
main.c:17:20: error: expected ')' before numeric constant
   17 |             box+=(a\10)%10;
      |                  ~ ^~~
      |                    )
main.c:21:19: error: stray '\' in program
   21 |             box+=a\1000;
      |                   ^
main.c:21:19: error: expected ';' before numeric constant
   21 |             box+=a\1000;
      |                   ^~~~~
      |                   ;
main.c:22:20: error: stray '\' in program
   22 |             box+=(a\100)%10;
      |                    ^
main.c:22:20: error: expected ')' before numeric constant
   22 |             box+=(a\100)%10;
      |                  ~ ^~~~
      |                    )
main.c:23:20: error: stray '\' in program
   23 |             box+=(a\10)%10;
      |                    ^
main.c:23:20: error: expected ')' before numeric constant
   23 |             box+=(a\10)%10;
      |                  ~ ^~~
      |                    )
main.c:27:19: error: stray '\' in program
   27 |             box+=a\100;
      |                   ^
main.c:27:19: error: expected ';' before numeric constant
   27 |             box+=a\100;
      |                   ^~~~
      |                   ;
main.c:28:20: error: stray '\' in program
   28 |             box+=(a\10)%10;
      |                    ^
main.c:28:20: error: expected ')' before numeric constant
   28 |             box+=(a\10)%10;
      |                  ~ ^~~
      |                    )
main.c:32:19: error: stray '\' in program
   32 |             box+=a\10;
      |                   ^
main.c:32:19: error: expected ';' before numeric constant
   32 |             box+=a\10;
      |                   ^~~
      |                   ;
main.c:39:19: error: stray '\' in program
   39 |             box+=b\10000;
      |                   ^
main.c:39:19: error: expected ';' before numeric constant
   39 |             box+=b\10000;
      |                   ^~~~~~
      |                   ;
main.c:40:20: error: stray '\' in program
   40 |             box+=(b\1000)%10;
      |                    ^
main.c:40:20: error: expected ')' before numeric constant
   40 |             box+=(b\1000)%10;
      |                  ~ ^~~~~
      |                    )
main.c:41:20: error: stray '\' in program
   41 |             box+=(b\100)%10;
      |                    ^
main.c:41:20: error: expected ')' before numeric constant
   41 |             box+=(b\100)%10;
      |                  ~ ^~~~
      |                    )
main.c:42:20: error: stray '\' in program
   42 |             box+=(b\10)%10;
      |                    ^
main.c:42:20: error: expected ')' before numeric constant
   42 |             box+=(b\10)%10;
      |                  ~ ^~~
      |                    )
main.c:46:19: error: stray '\' in program
   46 |             box+=b\1000;
      |                   ^
main.c:46:19: error: expected ';' before numeric constant
   46 |             box+=b\1000;
      |                   ^~~~~
      |                   ;
main.c:47:20: error: stray '\' in program
   47 |             box+=(b\100)%10;
      |                    ^
main.c:47:20: error: expected ')' before numeric constant
   47 |             box+=(b\100)%10;
      |                  ~ ^~~~
      |                    )
main.c:48:20: error: stray '\' in program
   48 |             box+=(b\10)%10;
      |                    ^
main.c:48:20: error: expected ')' before numeric constant
   48 |             box+=(b\10)%10;
      |                  ~ ^~~
      |                    )
main.c:52:19: error: stray '\' in program
   52 |             box+=b\100;
      |                   ^
main.c:52:19: error: expected ';' before numeric constant
   52 |             box+=b\100;
      |                   ^~~~
      |                   ;
main.c:53:20: error: stray '\' in program
   53 |             box+=(b\10)%10;
      |                    ^
main.c:53:20: error: expected ')' before numeric constant
   53 |             box+=(b\10)%10;
      |                  ~ ^~~
      |                    )
main.c:57:19: error: stray '\' in program
   57 |             box+=b\10;
      |                   ^
main.c:57:19: error: expected ';' before numeric constant
   57 |             box+=b\10;
      |                   ^~~
      |                   ;