/in/foo.c:6:5: error: variably modified 'a' at file scope
 int a[2*N][N];
     ^
/in/foo.c:6:5: error: variably modified 'a' at file scope
/in/foo.c:7:1: error: unknown type name 'bool'
 bool dp[2][N][M*2];
 ^~~~
/in/foo.c:7:6: error: variably modified 'dp' at file scope
 bool dp[2][N][M*2];
      ^~
/in/foo.c:7:6: error: variably modified 'dp' at file scope
/in/foo.c: In function 'main':
/in/foo.c:14:12: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
    a[i][j]=abs(a[i][j]);
            ^~~