View Compilation Error

0_0_21605634_4965.cpp: In function 'int main()':
0_0_21605634_4965.cpp:37:29: error: 'scanf' was not declared in this scope
     while(scanf("%d%d",&s,&t) != -1){
                             ^
0_0_21605634_4965.cpp:46:27: error: 'sort' was not declared in this scope
         sort(p+1,p+n+1,cmp);
                           ^
0_0_21605634_4965.cpp:50:37: error: 'swap' was not declared in this scope
                 swap(p[i].r,p[i-1].r);
                                     ^
0_0_21605634_4965.cpp:53:30: error: 'printf' was not declared in this scope
         printf("%d\n",n+num+1);
                              ^