C :

#include<stdio.h>
int main()
{
    int a,b,di;
    int sum,max;
    int day;
    while(scanf("%d",&day)!=EOF)
    {
      sum=0;
      max=sum;
      day--;
      scanf("%d",&a);
      while(day--)
      {
          scanf("%d",&b);
          di=b-a;
          if(sum<0) sum=di;
          else sum+=di;
          if(max<sum) max=sum;
          a=b;
      }
      printf("%d\n",max);
    }
return 0;
}

C++ :

#include<stdio.h>
#include<string.h>
int a[100000];
int main(){
  int n,i,j,k;
  while(scanf("%d",&n)!=EOF)
  {
      memset(a,0,sizeof(a));
      int count=0,sum=0;
      for(i=1;i<=n;i++)
        scanf("%d",&a[i]);
      for(i=1;i<n;i++)
      {
        k=i;
        for(j=i+1;j<=n;j++)
          if(a[k]<a[j]) k=j;
        count=a[k]-a[i];
        if(count>sum) sum=count;
      }
      printf("%d\n",sum);
  }
  return 0;
}