#include <stdio.h>

int N, D, S1, E1, L1, S2, E2, L2;
double A, arr[10001];

int main()
{
    int i, start = 0, end = 0, one, pos1 = 0, pos2 = 0;
    arr[0] = -1e10;

//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);


    scanf("%d %d %d %d %d %d %d %d %lf", &N, &D, &S1, &E1, &L1, &S2, &E2, &L2, &A);
    for (i = 1; i <= N; i++)
        scanf("%lf", &arr[i]);

    for (i = 1; i <= N; i++)
    {
        if (arr[i] <= 35) break;
    }

    for (++i; i <= N; i++)
    {
        if (arr[i] >= 95)
        {
            start = i;
            break;
        }
    }

    if (start == 0)
    {
        printf("No surface.\n");
        return 0;
    }
    else
    {
        printf("Surface found at %d.\n", start);
    }

    for (i = start; i <= N; i++)
    {
        arr[i] *= 1 + (i - start) * A;
    }


    for (i = start + 1; i <= N; i++)
    {
        if (arr[i] <= 35) break;
    }

    if (i < start + D) i = start + D;

    for (; i <= N; i++)
    {
        if (arr[i] >= 95)
        {
            end = i;
            break;
        }
    }

    if (end == 0)
    {
        printf("No bottom.\n");
        end = N;
    }
    else
    {
        printf("Bottom found at %d.\n", end - start);
    }

    S1 += start;
    E1 += start;
    if (E1 > end) E1 = end;
    one = 0;

    for (i = S1; i <= E1; i++)
    {
        one = 1;

        if (arr[i] > arr[pos1]) pos1 = i;
    }

    if (one == 0)
    {
        printf("Channel 1: No search.\n");
    }
    else
    {
        if (arr[pos1] >= L1) printf("Channel 1: Object at %d.\n", pos1 - start);
        else printf("Channel 1: No object.\n");
    }

    S2 += start;
    E2 += start;
    if (E2 > end) E2 = end;
    one = 0;

    for (i = S2; i <= E2; i++)
    {
        one = 1;

        if (arr[i] > arr[pos2]) pos2 = i;
    }

    if (one == 0)
    {
        printf("Channel 2: No search.\n");
    }
    else
    {
        if (arr[pos2] >= L2) printf("Channel 2: Object at %d.\n", pos2 - start);
        else printf("Channel 2: No object.\n");
    }

    return 0;
}

Object cannot be located on the back wall.

I think this should be put to problem statement because it tells that objects cannot be BEHIND the back wall (at least eng. version)