#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    int a;
    cin>>a;
    int b;
    cin>>b;
    int c;
    int tab[b];
    for(int i=0; i<b; i++)
    {
            cin>>tab[i];
            }
    for (int j=1; j<b; j++)
    {
        if (tab[j-1]-a<0) tab[j]=tab[j];
        else tab[j]=tab[j]+(tab[j-1]-a);

        }
    if (tab[b-1]-a<0) cout<<"0"<<endl;
    else cout<<(tab[b-1]-a)<<endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}

In dev-c++ it works...

Edited by author 11.07.2012 19:10

Error in this line
int tab[b];
Array size should be constant value.

The problem is that compiler on this website(Visual C++) has a little another syntax and you can't use such thing:
int b;
cin>>b;
int tab[b];
An array size in C++ must be initialized by a constant value, so you can't initialize it by a variable you read from the stream. Try use dynamic arrays in such cases.

Edited by author 12.07.2012 13:50