ois_duplicato

#include <stdio.h>
#include <algorithm>
#define MAXN 1000000

int trova(int N, int P[])
{
    int i=0, foglio, pos;
    while(i<(N*2)-1 && foglio!=0)
    {
        foglio = std::count(P,P+N,P[i]);
        pos = P[i];
        i++;
    }
    return pos;
}

int P [2*MAXN];

int main()
{
    FILE *fr, *fw;
    int N, i;
    fr = fopen("input.txt", "r");
    fw = fopen("output.txt", "w");
    fscanf(fr, "%d\n", &N);
    for(i=0; i<2*N-1; i++) fscanf(fr, "%d ", &P[i]);
    fprintf(fw, "%d", trova(N, P));
    fclose(fr);
    fclose(fw);
    return 0;
}