Example

int main(int argc, char* argv[])
{

int index = 2;

cout << argv[index];

return 0;
}

Solution
Make sure the value of the index variable is within the bounds of the array before using it.

int main(int argc, char* argv[])
{

int index = 2;

if( index>=0  &&  index< argc){
cout << argv[index];
}

return 0;
}