/in/foo.cc: In function 'void msort(int, int)':
/in/foo.cc:18:27: error: 'ans' was not declared in this scope
             c[k++]=a[j++],ans+=mid-i+1;
                           ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:50:15: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
             if(j%2)
               ^
/in/foo.cc:61:15: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
             if(j%2)
               ^