View Compilation Error

0_0_28905756_6904.cpp:5:11: error: 'N' was not declared in this scope
 int n,m,f[N],re[M],ca;
           ^
0_0_28905756_6904.cpp: In function 'int find(int)':
0_0_28905756_6904.cpp:8:9: error: 'f' was not declared in this scope
  return f[x]==x?x:f[x]=find(f[x]);
         ^
0_0_28905756_6904.cpp: In function 'int main()':
0_0_28905756_6904.cpp:13:25: error: 'f' was not declared in this scope
   for(int i=0; i<n; i++)f[i]=i,re[i]=i;
                         ^
0_0_28905756_6904.cpp:23:15: error: 'f' was not declared in this scope
     if(fx!=fy)f[fx]=fy;
               ^
0_0_28905756_6904.cpp:29:5: error: 'f' was not declared in this scope
     f[sham]=sham;
     ^