Language: C++

/*
...........__________                                                                           ___  __
.............|       |                                                                           |   /
.............|       |                                                                           |  /
.............|       |                               |                         __                | /      _______
.............|_______|  _______            _______   |______   ________   /|  /  |               |/       |      |
.............| \               | |      | |          |      |          | / | /   |               |\       |
.............|  \       _______| |      | |_______   |      |   _______|   |/    |               | \      |
.............|   \      |      | |      |         |  |      |  |       |   |     |               |  \     |
...........__|    \__|  |______| |______| ________|  |      |_ |_______|   |     |__|           _|   \__ _|        .

*/
#include<bits/stdc++.h>
using namespace std ;
#define int                 long long
#define ull                 unsigned long long int
#define ld                  long double
#define vi                  vector<int>
#define vii                 vector<pair<int,int>>
#define vvi                 vector<vector<int>>
#define pii                 pair<int,int>
#define prec(x)             fixed<<setprecision(15)<<x
#define all(x)              x.begin(),x.end()
#define rall(x)             x.rbegin(),x.rend()
#define rev(x)              reverse(x.begin(),x.end())
#define mset(a,b)           memset(a,b,sizeof(a))
#define mcpy(a,b)           memcpy(a,b,sizeof(a))
#define fo0(i,n)            for(int i=0,i##end=n;i<i##end;i++)
#define fo1(i,n)            for(int i=1,i##end=n;i<=i##end;i++)
#define fo(i,a,b)           for(int i=a,i##end=b;i<=i##end;i++)
#define foe(i,x)            for(__typeof((x).end())i=(x).begin();i!=(x).end();++i)
#define fre(i,x)            for(__typeof((x).rend())i=(x).rbegin();i!=(x).rend();++i)
#define fast ios_base::sync_with_stdio(false); cin.tie(0);cout.tie(0)
int gcd(int a, int b) { return b ? gcd(b, a%b) : a; }
#define inf 1e18
const int mod=1e9+7;
const int N=2e5+9;
int a[N],b[N];

void raushan_kumar(){

    //variables
    int d=0,e=0,f=0,g=0,h=0,i=0,j=0,k=0,l=0,m,n,o=0,p=0,q=0,r=0,u=0,v=0,w=0,x=0,y=0,z=0,s=0,t=0;
    double f1=0.0,f2=0.0,f3=0.0,f4=0.0,f5=0.0,f6=0.0;
    int flag=0,ans=0,res=0,cnt=0;

    string s;cin>>s;
    fo0(i,s.length()){
        if(s[i]=='7'){
            flag=1;
        }
    }
    if(flag)
        cout<<"Yes";
    else{
        cout<<"No";
    }
    
}

int32_t main()
{
    fast;int t=1;
    //cin>>t;
    while(t--){
        raushan_kumar();
    }

}


Compiler output:
a.cc: In function 'void raushan_kumar()':
a.cc:47:12: error: conflicting declaration 'std::string s'
   47 |     string s;cin>>s;
      |            ^
a.cc:43:89: note: previous declaration as 'long long int s'
   43 |     int d=0,e=0,f=0,g=0,h=0,i=0,j=0,k=0,l=0,m,n,o=0,p=0,q=0,r=0,u=0,v=0,w=0,x=0,y=0,z=0,s=0,t=0;
      |                                                                                         ^
a.cc:48:13: error: request for member 'length' in 's', which is of non-class type 'long long int'
   48 |     fo0(i,s.length()){
      |             ^~~~~~
a.cc:28:48: note: in definition of macro 'fo0'
   28 | #define fo0(i,n)            for(int i=0,i##end=n;i<i##end;i++)
      |                                                ^
a.cc:49:13: error: invalid types 'long long int[long long int]' for array subscript
   49 |         if(s[i]=='7'){
      |             ^