View Compilation Error

0_0_30289252_18079.cpp: In function 'int main()':
0_0_30289252_18079.cpp:24:5: error: 'f' was not declared in this scope
     f[a][b]++;
     ^
0_0_30289252_18079.cpp:30:5: error: 'f' was not declared in this scope
     f[i][l]=f[i][l-1]+cake[i][l];
     ^
0_0_30289252_18079.cpp:37:18: error: 'f' was not declared in this scope
    maxn=max(maxn,f[i][mt]);
                  ^