View Compilation Error

0_0_33936626_28746.cpp:3:14: error: 'b' was not declared in this scope
 int fs(int f[b])
              ^
0_0_33936626_28746.cpp: In function 'int fs(...)':
0_0_33936626_28746.cpp:6:5: error: 'f' was not declared in this scope
     f[b]=f[b-1]+2*f[b-2];
     ^
0_0_33936626_28746.cpp:6:7: error: 'b' was not declared in this scope
     f[b]=f[b-1]+2*f[b-2];
       ^