#include <stdio.h>
#include <assert.h>

bool binSearch(const int *a, int n, int x, int* index);

int main() {
    FILE* in = fopen("input.txt", "r");
    if (in == NULL) {
        perror("Cannot open input file");
        return -1;
    }
    int x;
    int n = 0;
    while (fscanf(in, "%d", &x) == 1) {
        ++n;
    }
    rewind(in);

    if (n < 1) {
        fprintf(stderr, "Empty input file.\n");
        return -1;
    }

    if (fscanf(in, "%d", &x) != 1) {
        fprintf(stderr, "Incorrect input file.\n");
        return -1;
    }
    --n;

    int *a = new int[n];

    int m = 0;
    for (int i = 0; i < n; ++i) {
        if (fscanf(in, "%d", &(a[i])) == 1) {
            ++m;
        }
    }
    fclose(in);

    int index;
    bool found = binSearch(a, m, x, &index);
    if (found)
        printf("Element is found, index=%d\n", index);
    else
        printf("Element is not found, index=%d.\n", index);

    FILE* out = fopen("output.txt", "w");
    if (in == NULL) {
        perror("Cannot open output file");
        return -1;
    }

    /*
    for (int i = 0; i < m; ++i) {
        if (i > 0) {
            if (i % 10 == 0)
                fprintf(out, "\n");
            else
                fprintf(out, " ");
        }
        fprintf(out, "%d", a[i]);
    }
    fprintf(out, "\n");
    */
    fprintf(out, "%d\n", index);

    fclose(out);
    return 0;
}

bool binSearch(   // Binary search in ordered array
    const int *a, // Pointer to the beginning of array
    int n,        // Number of elements in array
    int x,        // Element to find
    int *idx      // Result: *idx is such index that
                  //         a[*idx - 1] < x <= a[*idx]
) {               // Return value: true when x is found

    // Consider first the special cases
    if (n < 0) {               // Array is empty
        *idx = 0;
        return false;
    } else if (x <= a[0]) {    // x <= minimal element of array
        *idx = 0;
        return (x == a[0]);
    } else if (x > a[n-1]) {   // x > maximal element of array
        *idx = n;
        return false;

    } else {                   // General case
        assert(
           n > 0 &&
           a[0] < x && x <= a[n-1]
        );
        int i0 = 0;     // [i0, i1] is the current segment of array 
        int i1 = n-1;   //          that may contain x

        while (i1 - i0 > 1) {  // loop while the length of segment > 1
            assert(a[i0] < x && x <= a[i1]); // Invariant

            int c = (i0+i1)/2; //   Middle of the segment
            if (a[c] < x) {    //   if x > middle element
                i0 = c;        //     then select the right part
            } else {           //   else
                i1 = c;        //     select the left part
            }                  //   end if
        }                      // end loop
        assert(a[i1-1] < x && x <= a[i1]);

        *idx = i1;             // Write the resulting index
        return (x == a[i1]);   // Return true if x is found
    }
}