Cod sursă (job #676982)

#include <fstream>
#pragma GCC optimize ("O1")
#pragma GCC optimize ("O2")
#pragma GCC optimize ("O3")
#pragma GCC optimize ("O4")
#pragma GCC optimize ("unroll-loops")
#pragma GCC optimize ("Ofast")
using namespace std;
ifstream cin("bart.in");
ofstream cout("bart.out");
int pi[500005];
string s;
void build(int x)
{
    pi[x]=pi[x-1];
    while(pi[x]>0 && s[x]!=s[pi[x]+1])
        pi[x]=pi[pi[x]];
    if(s[x]==s[pi[x]+1])
        pi[x]++;
}
int main()
{
    cin>>s;
    s="#"+s;
    for(int i=2;i<s.size();i++)
        build(i);
    for(int i=1;i<s.size()-pi[s.size()-1];i++)
        cout<<s[i];
}