Language: C++

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<stack>
#include<unordered_set>
#include<cmath>
#include<tuple>
#include<numeric>
#include<iterator>
#include<set>
#include<unordered_map>
#include<map>
#include<queue>
#include<cstring>
#include<stdio.h>
#include<fstream>

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
#define foru(i , a , b) for(ll i = a ; i < b ; i++)
#define ford(i , a , b) for(ll i = a ; i >= b ; i--)
#define ain(a , n) for(ll i = 0 ; i < n ; i++) cin >> a[i]
#define aout(a , n) for(ll i = 0 ; i < n ; i++) cout << a[i] << " "
#define M 1000000007
#define mp make_pair
#define mt make_tuple
#define cend cout << "\n"
#define all(x) x.begin() , x.end()
#define aout2(a , n , m) for(ll i = 0 ; i < n ; i++){for(ll j = 0 ; j < m ; j++){cout << a[i][j] << " ";} cout << endl;}
#define ain2(a , n , m) for(ll i = 0 ; i < n ; i++){for(ll j = 0 ; j < m ; j++){cin >> a[i][j];}}
#define ff first
#define ss second
#define mset(a , b) memset(a , b , sizeof(a))
#ifndef ONLINE_JUDGE
#define dbg(a) cerr << #a << ": "; _print(a); cerr << endl;
#else
#define dbg(a) // No more TLEs
#endif

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector <int> vi;
typedef vector <ll> vll;
typedef vector <char> vch;
typedef vector <string> vs;
typedef set <ll> sll;
typedef multiset <ll> msll;
typedef pair <ll , ll> pll;
typedef vector <pair <ll , ll>> vpll;
template <class T, class V> void _print(pair <T, V> p){cerr << "{" << p.ff << "," << p.ss << "}";}
template <class T> void _print(vector <T> v){cerr << "[ "; for(T i: v) cerr << i << " "; cerr << "]";}
template <class T> void _print(set <T> s){cerr << "[ "; for(T i: s) cerr << i << " "; cerr << "]";}
template <class T> void _print(T n){cerr << n;}

/*----------------------------- # --- MATH ALGORITHMS --- # -----------------------------*/

template <class T> T gcd(T a , T b){ while(a != 0){T temp = a; a = b % a; b = temp;}return b;}
template <class T> T egcd(T a , T b , T &x , T &y){T gcd , xt , yt;if(a == 0){gcd = b;x = 0 , y = 1;}else {gcd = egcd(b % a , a , xt , yt);x = yt - (b/a)*xt; y = xt;}return gcd;}
template <class T> T expo(T base , T exp , T mod){T res = 1;base = base % mod;while (exp > 0){if (exp & 1)res = (res*base) % mod;exp = exp>>1;base = (base*base) % mod;}return res;}
template <class T> T modinv(T a , T mod){T x , y; egcd<T>(a , mod , x , y);while(x < 0) x += mod; while(x >= mod) x -= mod; return x;}
template <class T> T modinvfermat(T a , T mod){return expo<T>(a , mod - 2 , mod);}
template <class T> bool rev(T a , T b){return a > b;}
template <class T> ll maxpower(T a , T b){ll ans = 0;while(a > 0 && a % b == 0){ans++;a /= b;}return ans;}
template <class T> T mceil(T a, T b){if(a % b == 0) return a/b; else return a/b + 1;}
template <class T> T lcm(T a, T b){return (a*b)/gcd<T>(a, b);}

/*----------------------------- # --- MAIN CODE --- # -----------------------------*/

int main() {
    fastio;
#ifndef ONLINE_JUDGE
    freopen("testcase.txt", "r", stdin);
    freopen("error.txt", "w", stderr);
    freopen("output.txt", "w", stdout);
#endif
    ll a, b, cin >> a >> b;
    cout << a*b;
}









Compiler output:
a.cc: In function 'int main()':
a.cc:77:18: error: expected initializer before '>>' token
   77 |     ll a, b, cin >> a >> b;
      |                  ^~