Calculate two numbers and skip the sign?

I have the following situation: I calculate two values on the one side and two other values on the other side. Then I compare the two results, but in this comparison the sign doesn't matter for me. For example:

(1 - 2) == (2 - 1) - should tell me, that 1 == 1, not that -1 != 1

I can solve this by writing a function that gives me an absolute value back from the calculation, but maybe someone knows a better way.

For a better understanding I enclose my code, the important part is in the third if-statement:

#include <stdio.h>
#include <stdbool.h>
#define N 8

int abs(int x){
  if (x<0)
    return -x;
  return x;
}

bool gefahr(bool queen[N][N]){

  int dame1x=N+1;
  int dame1y=N+1;
  int dame2x=N+1;
  int dame2y=N+1;

  for(int i=0; i<N;i++){
    for(int j=0;j<N;j++){
     if(queen[i][j] && dame1x>N){
       dame1x=i;
       dame1y=j;
     } else if(queen[i][j] && dame2x>N) {
       dame2x=i;
       dame2y=j;
      }
    }
  }

  printf("Dame 1: %d %d\n",dame1x,dame1y);
  printf("Dame 2: %d %d\n",dame2x,dame2y);

  if(dame1x==dame2x){
    printf("Waagerecht bedroht\n");
    return true;
  }
  if(dame1y==dame2y){
    printf("Senkrecht bedroht\n");
    return true;
  }

  if(abs(dame2x-dame1x)==abs(dame2y-dame1y)){
    printf("Diagonal bedroht\n");
    return true;
  }
}

int main(){

  bool feld[N][N];

  for(int i=0; i<N;i++){
    for(int j=0;j<N;j++){
      feld[i][j]=false;
    }
  }
  feld[0][4]=true;
  feld[4][4]=true;
  gefahr(feld);
  feld[0][4]=false;
  feld[4][4]=false;

  feld[2][2]=true;
  feld[0][4]=true;
  gefahr(feld);
  feld[0][4]=false;
  feld[4][4]=false;

  feld[0][4]=true;
  feld[4][4]=true;
  gefahr(feld);

}

Thanks for your help!

Jan