Runtime Error when trying to submit an answer to URI online judge (C++)

My code works fine on Visual Studio but when i try to submit my code to URI i get runtime error...here's the link for the problem i am trying to slove hope this helps & thx in advance http://ift.tt/1DKv8nA

    #include <iostream>
using namespace std;
class LostBoots{
public:
    void intSwap(int *element1, int *element2){
        int temp = *element1;
        *element1 = *element2;
        *element2 = temp;
    }
    void charSwap(char *element1, char *element2){
        char temp = *element1;
        *element1 = *element2;
        *element2 = temp;
    }
    void sort(int arr[], char arcr[], int length){
        for (int i = 0; i < length - 1; i++){
            for (int j = i + 1; j < length; j++){
                if (arr[i] > arr[j]){
                    intSwap(&arr[i], &arr[j]);
                    charSwap(&arcr[i], &arcr[j]);
                }
            }
        }
    }
};
int main(){
    int N, M[60], count;
    char L[60];
    LostBoots boot;
    while (cin >> N){
        count = 0;
        for (int i = 0; i < N; i++){
            cin >> M[i] >> L[i];
        }
        boot.sort(M, L, N);
        for (int i = 0; i < N; i++){
            if (i % 2 == 0){
                if (M[i] == M[i + 1] && L[i] != L[i + 1])
                    count++;
            }
        }
        cout << count << endl;
    }
    return 0;
}