Crypt-generator

#include <fstream>
#include <cstring>
#include <vector>
using namespace std;
int i,j,m,n,diff;
vector<string>v;
string s;
int main()
{
  ifstream fi("crypt.in");
  ofstream fo("crypt2.out");
  fi>>n; getline(fi,s);
  for(i=1;i<=n;i++)
  {
    getline(fi,s);
    v.push_back(s);
  }
  for(i=1;i<=n;i++)
  {
    getline(fi,s);
    m=s.size();
    for(j=0;j<m;j++)
    {
      diff=v[i-1][j]-s[j];
      if(diff<0) diff=-diff;
      fo<<diff-1<<" ";
    }
    fo<<"\n";
  }

}