替换

replace

if（M [i] [j]< 0）

sum = sum + M [i] [j];

countn ++;

if (M[i][j]<0)
sum= sum + M[i][j];
countn++;

with

with

if (M[i][j]<0)
{
  sum= sum + M[i][j];
  countn++;
}