What's the problem with this Code?

The result is "fatal" on all the IARCS online judge.

By the way, what is "fatal"?

#include<iostream>
#include<cstdio>
#include<set>
#include<string>
#include<sstream>
using namespace std;
set<string> a;
int n;
int main()
{
    cin>>n;
    do
    {
        string s;
        getline(cin,s);
        for(int i=0;i<s.size();i++)
        {
            if(isalpha(s[i])) s[i]=tolower(s[i]);

What's the problem with this code?

It passed subtask 1, but got 4 WAs on subtask 2.

It first initializes the array "can", which marks if a cell is safe at the time Spiff could possibly reach it(if the coordinates of a cell is x,y, then it will take x+y-2 seconds). Then the DP checks if each cell could be accessed. If dp[n][m] is true, the shortest time is n+m-2, since Spiff has to go down n-1 steps and go right m-1 steps.

#include<iostream>
#include<cmath>
#include<cstring>
using namespace std;
int n,m,k;
bool can[2510][2510];
bool dp[2510][2510];
int x,y,s,f;
int dist;
int dist2;
int main()
{

I've come across a tricky binary search problem. There is an n*n array of different heights, and the cost of moving from one coordinate in the array to an adjacent one(up, down,left,right) is the difference of their heights. The problem asks for the minimum cost to traverse half of the coordinates(rounded up if the size of the array is odd). My program searches for the answer between 1 and the sum of all the coordinates' heights.

here is my pseudocode

let l be 1

let r be the sum of of all the coordinates' heights

while l<r

let mid be (l+r)/2

if half of the array can be traversed with a cost that is smaller than or. equal to mid

r=mid

else