The following code (problem B of last contest) give different outputs if compiled with different versions of C++11/C++14, only on this specific input

42147 412393322

why is that?

(I included the header only for reference)

//START HEADER ---------------------------------------------

using namespace std;
#define int int64_t
#define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define EPS 1e-7
#define INF 1e9
#define foor(n) for (int i=0;i<n;i++)
#define fooor(a,n) for (int i=a;i<n;i++)
#define per(a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define ssz(x) ((int)(x).size())
#define pc(x) putchar(x)
//#define PI acos(-1);
typedef pair<int,int> ii;
typedef vector<int> vi;
typedef vector<pair<int,int>> vii;
typedef vector<vector<int>> vvi;
typedef long long ll;
typedef unsigned long long ull;
const ll mod=1000000007;
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
namespace ib {char b[100];}
inline void pi(int x){ //fasto
    if(x==0) {pc(48); return;}
    if(x<0) {pc('-'); x=-x;}
    char *s=ib::b;
    while(x) *(++s)=x%10,x/=10;
    while(s!=ib::b) pc((*(s--))+48);
}
inline void ri(int &x){ //fasti
    x=0; static char c; bool t(0);
    while(c=getchar(),c<'0'||c>'9') if(c=='-') t=1; else t=0;
    do x=(x<<1)+(x<<3)+c-'0'; while(c=getchar(),c>='0'&&c<='9');
    if(t) x=-x;
}
//#define cerr if(0)cerr
#define error(args...) { vector<string> _v = split(#args, ','); err(_v.begin(), args); }
vector<string> split(const string& s, char c) {
    vector<string> v;
    stringstream ss(s);
    string x;
    while (getline(ss, x, c))
        v.emplace_back(x);
    return move(v);
}
void err(vector<string>::iterator it) {}
template<typename T, typename... Args>
void err(vector<string>::iterator it, T a, Args... args) {
    cerr << it -> substr((*it)[0] == ' ', it -> length()) << " = " << a << '\n';
    err(++it, args...);
}

// FINISH HEADER ---------------------------------------------------------------------------------------

string itoa(int n){
    string res = "";
    int r=-1;
    while(n/10!=0){
        r=n%10;
        res+=char(r+'0');
        n/=10;
    }
    r=n%10;
    res+=char(r+'0');
    reverse(all(res));
    return res;
}

int aatoi(string s){
    int res=0;
    foor(ssz(s)){
        res+=(int)(s[i]-'0')*pow(10, i);
    }
    //   error(s,res);
    return res;
    
}


int32_t main(){
    int n,m;
    cin >> n >> m;
    int res=0;
    foor(n+1){
        
        string s = itoa(i);
        string r = s;
        reverse(all(r));
        s=s+r;
        //error(aatoi(s.c_str()));
        res+=aatoi(s.c_str());
    }
    return cout<<res% (1ll * m),0;
}