//prob 1

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i,n,v[100],sum,sumT=0;

    scanf("%d",&n);

    for (i=0; i<n-1; i++)
        {
            scanf("%d",&v[i]);
            sumT+=v[i];
        }

    sum = (n*(n+1))/2;

    printf("Numarul lipsa este %d",sum-sumT);

    return 0;
}

//prob 2, metoda votului majoritar
#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i,n,v[100];

    scanf("%d",&n);

    for (i=0; i<n; i++)
        {
            scanf("%d",&v[i]);
        }

    int cand = v[0], k= 0 ;

    for (i=0; i<n-1; i++)
    {
        if (v[i] == v[i+1])
            k++;

        if ((v[i] != v[i+1]) && k == 0 )
        {
            cand = v[i+1];
            k--;
        }
    }

    printf("\n\n cand = %d  k = %d \n\n\n",cand,k);

    int nr_app = 0;

    for (i=0; i<n; i++)
    {
        if (v[i] == cand)
            nr_app++;
    }

    if (nr_app >= floor(n/2) + 1)
        printf("Elementul majoritar este %d.",cand);
    else
        printf("Nu exista un element majoritar.");





    return 0;
}

//prob 4
#include <stdio.h>
#include <stdlib.h>

int cautareBinare(int v[], int a, int b, int x)
{
    int mij;

    if (b >= a)
    {
        mij = a + (b - a)/2;

        if (v[mij] == x)
            return mij;

        if (v[mij] > x)
            return cautareBinare(v,a,mij-1,x);

        return cautareBinare(v,mij+1,b,x);
    }

    return -1;
}

int main()
{
    int i,n,v[100];

    scanf("%d",&n);

    for (i=0; i<n; i++)
        {
            scanf("%d",&v[i]);
        }

    printf("Elementul cautat se afla pe pozitia %d",cautareBinare(v,0,n-1,3));



    return 0;
}

//problema 4
#include <stdio.h>
#include <stdlib.h>

int cmmdc(int a, int b)
{
    if (a == 0)
        return b;

    return cmmdc(b%a,a);
}


int vector_cmmdc(int v[], int n)
{
    int i, div = 0;

    div = cmmdc(v[0],v[1]);
    if (div == 1)
            return 1;

    for (i=2; i<n; i++)
        div = cmmdc(div,v[i]);

    return div;
}


int cmmdc_rec(int v[], int n)
{
    if (n==2)
        return cmmdc(v[0],v[1]);
    else
        return cmmdc(cmmdc_rec(v,n-1),v[n-1]);
}

int main()
{
    int i,n,v[100];

    scanf("%d",&n);

    for (i=0; i<n; i++)
        {
            scanf("%d",&v[i]);
        }

    printf("cmmdcul este %d",cmmdc_rec(v,n));

    return 0;
}

//problema 5
#include <stdio.h>
#include <stdlib.h>
int suma(int *v, int n,int i)
{if(i==n)return 0;
    if(i%2==0)return v[i]+suma(v,n,i+1);
else return suma(v,n,i+1)-v[i];


}
int main()
{
    int v[100],n,i;
    scanf("%d",&n);
    for(i=0;i<n;i++)
        scanf("%d",&v[i]);
    printf("%d",suma(v,n,0));


    return 0;
}