View Compilation Error

0_0_17468000_20043.cpp:12:44: error: 'M' was not declared in this scope
 int n,cnt,m,t,u1[N],v1[N],dep[N],head[N],z[M];
                                            ^
0_0_17468000_20043.cpp: In function 'void init()':
0_0_17468000_20043.cpp:23:17: error: 'z' was not declared in this scope
   vis[i]=dep[i]=z[i]=fa[i]=u1[i]=v1[i]=0;
                 ^
0_0_17468000_20043.cpp: In function 'void tarjan(int)':
0_0_17468000_20043.cpp:43:4: error: 'z' was not declared in this scope
    z[i]=find(v1[i]);
    ^
0_0_17468000_20043.cpp:45:4: error: 'z' was not declared in this scope
    z[i]=find(u1[i]);
    ^
0_0_17468000_20043.cpp: In function 'int main()':
0_0_17468000_20043.cpp:79:45: error: 'z' was not declared in this scope
   printf("%d\n",dep[u1[i]]+dep[v1[i]]-2*dep[z[i]]);
                                             ^