Language: C++

#include<iostream>
using namespace std;
int main(){
int a,b,c,d;
  unsigned long s;
  cin>>a;
  b=a/15;
  s=b*(b+1)/2*225+60*b;
  c=a%15;
  s+=225*b;
  for (int i=1;i<=c;i++){
    switch(i){
    case '1'd+=1;break;
    case '2'd+=2;break;
    case '4'd+=4;break;
    case '7'd+=7;break;
    case '8'd+=8;break;
    case '11'd+=11;break;
    case '13'd+=13;break;
    case '14'd+=14;break;
    case '1'd+=1;break;}
  }
  cout<<s+d;
  
}


Compiler output:
a.cc:18:10: warning: multi-character character constant [-Wmultichar]
   18 |     case '11'd+=11;break;
      |          ^~~~~
a.cc:19:10: warning: multi-character character constant [-Wmultichar]
   19 |     case '13'd+=13;break;
      |          ^~~~~
a.cc:20:10: warning: multi-character character constant [-Wmultichar]
   20 |     case '14'd+=14;break;
      |          ^~~~~
a.cc: In function 'int main()':
a.cc:13:10: error: unable to find character literal operator 'operator""d' with 'char' argument
   13 |     case '1'd+=1;break;
      |          ^~~~
a.cc:13:17: error: expected ':' before ';' token
   13 |     case '1'd+=1;break;
      |                 ^
      |                 :
a.cc:14:10: error: unable to find character literal operator 'operator""d' with 'char' argument
   14 |     case '2'd+=2;break;
      |          ^~~~
a.cc:14:17: error: expected ':' before ';' token
   14 |     case '2'd+=2;break;
      |                 ^
      |                 :
a.cc:15:10: error: unable to find character literal operator 'operator""d' with 'char' argument
   15 |     case '4'd+=4;break;
      |          ^~~~
a.cc:15:17: error: expected ':' before ';' token
   15 |     case '4'd+=4;break;
      |                 ^
      |                 :
a.cc:16:10: error: unable to find character literal operator 'operator""d' with 'char' argument
   16 |     case '7'd+=7;break;
      |          ^~~~
a.cc:16:17: error: expected ':' before ';' token
   16 |     case '7'd+=7;break;
      |                 ^
      |                 :
a.cc:17:10: error: unable to find character literal operator 'operator""d' with 'char' argument
   17 |     case '8'd+=8;break;
      |          ^~~~
a.cc:17:17: error: expected ':' before ';' token
   17 |     case '8'd+=8;break;
      |                 ^
      |                 :
a.cc:18:10: error: unable to find character literal operator 'operator""d' with 'int' argument
   18 |     case '11'd+=11;break;
      |          ^~~~~
a.cc:18:19: error: expected ':' before ';' token
   18 |     case '11'd+=11;break;
      |                   ^
      |                   :
a.cc:19:10: error: unable to find character literal operator 'operator""d' with 'int' argument
   19 |     case '13'd+=13;break;
      |          ^~~~~
a.cc:19:19: error: expected ':' before ';' token
   19 |     case '13'd+=13;break;
      |                   ^
      |                   :
a.cc:20:10: error: unable to find character literal operator 'operator""d' with 'int' argument
   20 |     case '14'd+=14;break;
      |          ^~~~~
a.cc:20:19: error: expected ':' before ';' token
   20 |     case '14'd+=14;break;
      |                   ^
      |                   :
a.cc:21:10: error: unable to find character literal operator 'operator""d' with 'char' argument
   21 |     case '1'd+=1;break;}
      |          ^~~~
a.cc:21:17: error: expected ':' before ';' token
   21 |     case '1'd+=1;break;}
      |                 ^
      |                 :