Go: package main

import "fmt"

func main() {
	week := []string{"sun", "mon", "tue", "wed", "thu", "fri", "sat"}

	var day int
	fmt.Scan(&day)
	fmt.Println(week[(day+4)%7])//土曜日が9日という基準に揃えるために+4
}

C++: #include "bits/stdc++.h"
using namespace std;
typedef long long ll;
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) _repi(i,0,n)
#define _repi(i,a,b) for(ll i=a;i<b;++i)
#define rep(...) _overload3(__VA_ARGS__,_repi,_rep)(__VA_ARGS__)
#define _rrepi(i,a,b) for(ll i=b-1;i>=a;i--)
#define _rrep(i,n) _rrepi(i,0,n)
#define rrep(...) _overload3(__VA_ARGS__,_rrepi,_rrep)(__VA_ARGS__)
#define sum(...) accumulate(range(__VA_ARGS__),0)
#define _range(i) (i).begin(),(i).end()
#define _rangek(i,k) (i).begin(),(i).begin()+k
#define range(...) _overload3(__VA_ARGS__,a,_rangek,_range)(__VA_ARGS__)
#define LINF (ll)1000000000000000000
#define MOD (ll)1000000007
#define INF (int)1000000007
#define Yes(i) out(i?"Yes":"No")
#define YES(i) out(i?"YES":"NO")
#define INT(...) int __VA_ARGS__;in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;in(__VA_ARGS__)
#define STR(...) string __VA_ARGS__;in(__VA_ARGS__)
#define CHR(...) char __VA_ARGS__;in(__VA_ARGS__)
#define DBL(...) double __VA_ARGS__;in(__VA_ARGS__)
#define vec(type,name,size) vector<type> name(size);
#define VEC(type,name,size) vector<type> name(size);in(name)
struct aaa{aaa(){cin.tie(0); cout.tie(0); ios::sync_with_stdio(0); cout<<fixed<<setprecision(15);};}aaaaaaa;
inline void in() {}
template<typename T>
istream& operator >> (istream& is, vector<T>& vec);
template<typename T,typename L>
istream& operator >> (istream& is, pair<T,L>& p);
template<typename T>
ostream& operator << (ostream& os, vector<T>& vec);
template<typename T,typename L>
ostream& operator << (ostream& os, pair<T,L>& p);
template<typename T>
istream& operator >> (istream& is, vector<T>& vec){for(T& x: vec) is >> x;return is;}
template<typename T,typename L>
istream& operator >> (istream& is, pair<T,L>& p){is >> p.first;is >> p.second;return is;}
template<typename T>
ostream& operator << (ostream& os, vector<T>& vec){os << vec[0];rep(i,1,vec.size()){os << ' ' << vec[i];}return os;}
template<typename T,typename L>
ostream& operator << (ostream& os, pair<T,L>& p){os << p.first << " " << p.second;return os;}
template <class Head, class... Tail>
inline void in(Head&& head,Tail&&... tail){cin>>head;in(move(tail)...);}
template <class T>
inline void out(T t){cout<<t<<'\n';}
template <class Head, class... Tail>
inline void out(Head head,Tail... tail){cout<<head<<' ';out(move(tail)...);}


int main(){
    INT(a);
    a%=7;
    if(a==0)out("thu");
    else if(a==1)out("fri");
    else if(a==2)out("sat");
    else if(a==3)out("sun");
    else if(a==4)out("mon");
    else if(a==5)out("tue");
    else out("wed");
}

C++: #include <iostream>
using namespace std;
int main()
{
    int X;
    cin>>X;

    switch (X%7)
    {
    case 0/* constant-expression */:
        cout<<"thu"<<endl;
        break;
    
    case 1:
        cout<<"fri"<<endl;
        break;
    case 2:
        cout<<"sat"<<endl;
        break;
    case 3:
        cout<<"sun"<<endl;
        break;
    case 4:
        cout<<"mon"<<endl;
        break;
    case 5:
        cout<<"tue"<<endl;
        break;
    case 6:
        cout<<"wed"<<endl;
        break;
    }
    return  0;
}

C++: #include <iostream>
#include <algorithm>
#include <math.h>
#include <cmath>
#include <stdio.h>
#include <cstring>
#include <string.h>
#include <string>
#include <sstream>
#include <iomanip>

using namespace std;

int main (void)
{
	int n;
	cin >> n;
	
	if (n == 2 || n % 7 == 2)
	{
		cout << "sat" << endl;
	}
	else if (n == 3 || n % 7 == 3)
	{
		cout << "sun" << endl;
	}
	else if (n == 4 || n % 7 == 4)
	{
		cout << "mon" << endl;
	}
	else if (n == 5 || n % 7 == 5)
	{
		cout << "tue" << endl;
	}
	else if (n == 6 || n % 7 == 6)
	{
		cout << "web" << endl;
	}
	else if (n == 0 || n % 7 == 0)
	{
		cout << "thu" << endl;
	}
	else if (n == 1 || n % 7 == 1)
	{
		cout << "fri" << endl;
	}
}

C++: #include <iostream>
using namespace std;

int main(){
    int x;
    cin>>x;
    x%=7;
    switch(x){
        case 0:
            cout<<"thu"<<endl;
            break;
        case 1:
            cout<<"fri"<<endl;
            break;
        case 2:
            cout<<"sat"<<endl;
            break;
        case 3:
            cout<<"sun"<<endl;
            break;
        case 4:
            cout<<"mon"<<endl;
            break;
        case 5:
            cout<<"tue"<<endl;
            break;
        case 6:
            cout<<"wed"<<endl;
    }
    return 0;
}

C++: #include <iostream>
using namespace std;
int main(){
	int a;
	cin>>a;
	if (a%7==0) cout<<"thu"<<endl;
	if (a%7==1) cout<<"fri"<<endl;
	if (a%7==2) cout<<"sat"<<endl;
	if (a%7==3) cout<<"sun"<<endl;
	if (a%7==4) cout<<"mon"<<endl;
	if (a%7==5) cout<<"tue"<<endl;
	if (a%7==6) cout<<"wed"<<endl;
	return 0;
}

C++: #include<stdio.h>
int main()
{
	int x,r;
	scanf("%d",&x);
	r=x%7;
	switch(r){
	case 1:
		printf("fri\n");
		break;
	case 2:
		printf("sat\n");
		break;
	case 3:
		printf("sun\n");
		break;
	case 4:
		printf("mon\n");
		break;
	case 5:
		printf("tue\n");
		break;
	case 6:
		printf("wed\n");
		break;
	default:
		printf("thu\n");
	}
    return 0;
}

C++: #include<iostream>
using namespace std;
int main(){
	int a;
	cin >> a;
	switch (a % 7){
	case 0:
		cout << "thu"<<endl;
		break;
	case 1:
		cout << "fri" << endl;
		break;
	case 2:
		cout << "sat" << endl;
		break;
	case 3:
		cout << "sun" << endl;
		break;
	case 4:
		cout << "mon" << endl;
		break;
	case 5:
		cout << "thu" << endl;
		break;
	case 6:
		cout << "wed" << endl;
		break;
	}
	return 0;
}

C++: X = int(input())
if(X % 7 == 0):
    print("thu")
elif(X % 7 == 1):
    print("fri")
elif(X % 7 == 2):
    print("sat")
elif(X % 7 == 3):
    print("sun")
elif(X % 7 == 4):
    print("mon")
elif(X % 7 == 5):
    print("tue")
elif(X % 7 == 6):
    print("wed")

C++: #include<stdio.h>
int main(void)
{
	int x;
	scanf("%d\n",&x);
	if(x==4||x==11||x==18||x==25){
		printf("mon\n");
	}
	else if(x==5||x==12||x==19||x==26){
		printf("tue\n");
	}
	else if(x==6||x==13||x==20||x==27){
		printf("wed\n");
	}
	else if(x==7||x==14||x==21||x==28){
		printf("thu\n");
	}
	else if(x==1||x==8||x==15||x==22||x==29){
		printf("fri\n");
	}
	else if(x==2||x==9||x==16||x==23||x==30){
		printf("sat\n");
	}
	else{
		printf("sun\n");
	}
return 0;
}

C++: #define _USE_MATH_DEFINES
#include<bits/stdc++.h>
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
#define Rep(i,a,b) for(int i=0;i<b;i++)
#define REP(i,a,b) for(int i=0;i<=b;i++)
#define rev(i,n) for(int i=n-1;i>=0;i--)
#define vi vector<int>
#define vvi vector<vi>
#define pb push_back
#define pi pair<int,int>
#define vp vector<pair<int,int>>
#define mp make_pair
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
#define MEMSET(a) memset(a,0,sizeof(a))
#define inf (1ll<<60)
#define Yes(f) cout <<(f?"Yes":"No")<<endl//fが真の場合Yesを出力、偽の場合Noを出力
#define yes(f) cout <<(f?"yes":"no")<<endl
#define YES(f) cout <<(f?"YES":"NO")<<endl
#define SORT(v) sort(all(v))
#define RSORT(v) sort(all(v),greater<int>())

using namespace std;

const int mod=1e9+7;



signed main(){
    int x;
    cin >> x;
    x=x%7;

        if(x==0)
        {
            cout << "thu" << endl;
        }
        if(x==1)
        {
            cout<<"fri"<<endl;
        }
        if(x==2)
        {
            cout << "sat" <<endl;
        }
        if(x==3)
        {
            cout << "sun" << endl;
        }
        if(x==4)
        {
            cout << "mon" << endl;
        }
        if(x==5)
        {
            cout << "tue" << endl;
        }
        if(x==6)
        {
            cout << "wed" << endl;
        }
    return 0;
}