View Compilation Error

0_0_16466032_1912.cpp: In function 'int gao()':
0_0_16466032_1912.cpp:39:26: error: 'islower' was not declared in this scope
         if(islower(str[i])){
                          ^
0_0_16466032_1912.cpp: In function 'int main()':
0_0_16466032_1912.cpp:65:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&n) && n){
                        ^
0_0_16466032_1912.cpp:74:31: error: 'strlen' was not declared in this scope
         int len = strlen(str+1);
                               ^
0_0_16466032_1912.cpp:83:44: error: 'next_permutation' was not declared in this scope
         }while(next_permutation(id+1,id+1+n));
                                            ^
0_0_16466032_1912.cpp:84:25: error: 'puts' was not declared in this scope
         if(ok)puts("YES");
                         ^
0_0_16466032_1912.cpp:85:23: error: 'puts' was not declared in this scope
         else puts("NO");
                       ^