Language: C++

#include <bits/stdc++.h>
#include <cmath>
#include <set>
#include <cstdio>
#include <vector>
#include <iostream>
#include <utility>
 
#define fir first
#define sec second
#define get(n) scanf("%d",&n);
#define gets(s) string s;cin >> (s);
#define All(s) (s).begin(), (s).end()
#define chmin(x, y) x = min(x, y);
#define chmax(x, y) x = max(x, y);
#define rep(i, j) for (int (i)=0;(i)<(j);(i)++)
#define repk(i, j, k) for(int (i)=(j);(i)<(k);(i)++)
#define repdown(i, j, k) for(int (i)=(j);(i)>=(j);(i)--)
#define dump(x)  std::cout << #x << " = " << (x) << std::endl;
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#define vi vector<int> 
#define vvi vector<vector<int> >
using namespace std;
 
typedef unsigned long long int ll;
const int Mod = 1e9 + 7;
const int max_n = 3 * 1e5 + 1;
const ll INF = 10241024;
long double INFD = 100100100;
 
//_________template______________
inline void IN(void){
  return;
}
 
template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}
 
inline void OUT(void){
  cout << "\n";
  return;
}
 
template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}
 
//_____________________　following sorce code_________________________//
string s;
void input(){
  IN(s);
}
 
void solve(){
  input();
  if(s == "SUN")cout << 7;
  else if(s == "MON") cout << 6;
  else if(s == "TUE") cout << 5;
  else if(s == "WED") cout << 4;
  else if(s == "THU") cout << 3;
  else if(s == "FRI") cout << 2;
  else if(s == "SUT") cout << 1;
 
  cout << endl;
 
}
 
int main () {
    solve();
    return 0;
}
 
#include <bits/stdc++.h>
#include <cmath>
#include <set>
#include <cstdio>
#include <vector>
#include <iostream>
#include <utility>
 
#define fir first
#define sec second
#define get(n) scanf("%d",&n);
#define gets(s) string s;cin >> (s);
#define All(s) (s).begin(), (s).end()
#define chmin(x, y) x = min(x, y);
#define chmax(x, y) x = max(x, y);
#define rep(i, j) for (int (i)=0;(i)<(j);(i)++)
#define repk(i, j, k) for(int (i)=(j);(i)<(k);(i)++)
#define repdown(i, j, k) for(int (i)=(j);(i)>=(j);(i)--)
#define dump(x)  std::cout << #x << " = " << (x) << std::endl;
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#define vi vector<int> 
#define vvi vector<vector<int> >
using namespace std;
 
typedef unsigned long long int ll;
const int Mod = 1e9 + 7;
const int max_n = 3 * 1e5 + 1;
const ll INF = 10241024;
long double INFD = 100100100;
 
//_________template______________
inline void IN(void){
  return;
}
 
template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}
 
inline void OUT(void){
  cout << "\n";
  return;
}
 
template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}
 
//_____________________　following sorce code_________________________//
string s;
void input(){
  IN(s);
}
 
void solve(){
  input();
  if(s == "SUN")cout << 7;
  else if(s == "MON") cout << 6;
  else if(s == "TUE") cout << 5;
  else if(s == "WED") cout << 4;
  else if(s == "THU") cout << 3;
  else if(s == "FRI") cout << 2;
  else if(s == "SAT") cout << 1;
 
  cout << endl;
 
}
 
int main () {
    solve();
    return 0;
}

Compiler output:
a.cc:105:11: error: redefinition of 'const int Mod'
  105 | const int Mod = 1e9 + 7;
      |           ^~~
a.cc:26:11: note: 'const int Mod' previously defined here
   26 | const int Mod = 1e9 + 7;
      |           ^~~
a.cc:106:11: error: redefinition of 'const int max_n'
  106 | const int max_n = 3 * 1e5 + 1;
      |           ^~~~~
a.cc:27:11: note: 'const int max_n' previously defined here
   27 | const int max_n = 3 * 1e5 + 1;
      |           ^~~~~
a.cc:107:10: error: redefinition of 'const ll INF'
  107 | const ll INF = 10241024;
      |          ^~~
a.cc:28:10: note: 'const ll INF' previously defined here
   28 | const ll INF = 10241024;
      |          ^~~
a.cc:108:13: error: redefinition of 'long double INFD'
  108 | long double INFD = 100100100;
      |             ^~~~
a.cc:29:13: note: 'long double INFD' previously defined here
   29 | long double INFD = 100100100;
      |             ^~~~
a.cc:111:13: error: redefinition of 'void IN()'
  111 | inline void IN(void){
      |             ^~
a.cc:32:13: note: 'void IN()' previously defined here
   32 | inline void IN(void){
      |             ^~
a.cc:116:6: error: redefinition of 'template<class First, class ... Rest> void IN(First&, Rest& ...)'
  116 | void IN(First& first, Rest&... rest){
      |      ^~
a.cc:37:6: note: 'template<class First, class ... Rest> void IN(First&, Rest& ...)' previously declared here
   37 | void IN(First& first, Rest&... rest){
      |      ^~
a.cc:122:13: error: redefinition of 'void OUT()'
  122 | inline void OUT(void){
      |             ^~~
a.cc:43:13: note: 'void OUT()' previously defined here
   43 | inline void OUT(void){
      |             ^~~
a.cc:128:6: error: redefinition of 'template<class First, class ... Rest> void OUT(First, Rest ...)'
  128 | void OUT(First first, Rest... rest){
      |      ^~~
a.cc:49:6: note: 'template<class First, class ... Rest> void OUT(First, Rest ...)' previously declared here
   49 | void OUT(First first, Rest... rest){
      |      ^~~
a.cc:135:8: error: redefinition of 'std::string s'
  135 | string s;
      |        ^
a.cc:56:8: note: 'std::string s' previously declared here
   56 | string s;
      |        ^
a.cc:136:6: error: redefinition of 'void input()'
  136 | void input(){
      |      ^~~~~
a.cc:57:6: note: 'void input()' previously defined here
   57 | void input(){
      |      ^~~~~
a.cc:140:6: error: redefinition of 'void solve()'
  140 | void solve(){
      |      ^~~~~
a.cc:61:6: note: 'void solve()' previously defined here
   61 | void solve(){
      |      ^~~~~
a.cc:154:5: error: redefinition of 'int main()'
  154 | int main () {
      |     ^~~~
a.cc:75:5: note: 'int main()' previously defined here
   75 | int main () {
      |     ^~~~