大佬求助，vs运行成功，洛谷编译失败

#include <iostream>
#include <string.h>
using namespace std;
void add(char M[], int N)   //十进制以内
{
    char M1[108];
    strcpy(M1, M);
    strrev(M1);
    int c = 0;
    for (int i = 0;M1[i] != '\0' || c == 1;i++)
    {
        if (c == 1 && M1[i] == '\0')
        {
            M[i] = 1 + '0';
            M[i + 1] = '\0';
            break;
        }
        if ((M1[i] - '0') + (M[i] - '0') + c >= N)
        {
            M[i] = ((M[i] - '0') + (M1[i] - '0') - N + c) + '0';
            c = 1;
        }
        else
        {
            M[i] = ((M[i] - '0') + (M1[i] - '0') + c) + '0';
            c = 0;
        }
    }
}
void add16(char M[])  //十六进制
{
    char M1[108];
    strcpy(M1, M);
    strrev(M1);
    int c = 0;
    for (int i = 0;M1[i] != '\0' || c == 1;i++)
    {
        if (c == 1 && M1[i] == '\0')
        {
            M[i] = 1 + '0';
            M[i + 1] = '\0';
            break;
        }
        if (int(M[i]) <= 57 && int(M1[i]) <= 57)
        {
            if (((int(M[i])) - 48) + ((int(M1[i])) - 48) + c <= 9)
            {
                M[i] = char(((int(M[i])) - 48) + ((int(M1[i])) - 48) + c + 48);
                c = 0;
            }
            else if (((int(M[i])) - 48) + ((int(M1[i])) - 48) + c <= 15)
            {
                M[i] = char(((int(M[i])) - 48) + ((int(M1[i])) - 48) + c + 55);
                c = 0;
            }
            else
            {
                M[i] = char(((int(M[i])) - 48) + ((int(M1[i])) - 48) + c + 55);
                c = 1;
            }
        }
        else if (int(M1[i]) >= 65 && int(M[i]) >= 65)
        {
            if (((int(M[i])) - 55) + ((int(M1[i])) - 55) + c - 16 <= 9)
            {
                M[i] = char(((int(M[i])) - 55) + ((int(M1[i])) - 55) + c - 16 + 48);
                c = 1;
            }
            else
            {
                M[i] = char(((int(M[i])) - 55) + ((int(M1[i])) - 55) + c - 16 + 55);
                c = 1;
            }
        }
        else
        {
            if (((int(M[i])) - 48) + ((int(M1[i])) - 55) + c <= 15)
            {
                M[i] = char(((int(M[i])) - 48) + ((int(M1[i])) - 55) + c + 55);
                c = 0;
            }
            else
            {
                M[i] = char(((int(M[i])) - 48) + ((int(M1[i])) - 55) + c - 16 + 48);
                c = 1;
            }
        }
    }
}
int main()
{
    int N;
    char M[108];
    cin >> N;
    cin >> M;
    int i;
    char L[108];
    for (i = 0;i <= 29;i++)
    {
        if (N <= 10)
        {
            add(M, N);
        }
        else
        {
            add16(M);
        }
        strcpy(L, M);
        strrev(L);
        if (strcmp(L, M) == 0)
        {
            break;
        }
    }
    if (i <= 29)
    {
        cout << "STEP=" << i + 1;
    }
    else
    {
        cout << "Impossible!";
    }
    return 0;
}