View Compilation Error

0_0_28410962_13931.cpp: In function 'int main()':
0_0_28410962_13931.cpp:42:4: error: 'x' was not declared in this scope
    x=gi();  s1.push(x);
    ^
0_0_28410962_13931.cpp:46:4: error: 'x' was not declared in this scope
    x=gi(); printf("%d\n",f[x]);
    ^
0_0_28410962_13931.cpp:62:8: error: 'x' was not declared in this scope
   else{x=gi(); printf("%d\n",f[x]);}
        ^