Lucky numbers

input/code.cpp: In function 'int main()':
input/code.cpp:19:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i=1; i<s.size(); ++i){
                          ^

#include <iostream>
using namespace std;
string s;


int md[101][10][7];

int main(){
  for (int i=0; i<101; ++i) for (int j=0; j<10; ++j) for (int k=0; k<7; ++k) md[i][j][k]=1222333444;
  
  cin >> s;
  for (int d=1; d<=9; ++d){
    if (s[0]==d+'0'){
      md[0][d][d%7]=0;
    }else{
      md[0][d][d%7]=1;      
    }
  }
  for (int i=1; i<s.size(); ++i){
    for (int d=0; d<=9; ++d){
      int p=1;
      if (s[i]==d+'0') p=0;
      for (int e=0; e<=9; ++e){
	if (e+d==0 || e+d==7 || e+d==14){
	  for (int m=0; m<7; ++m){
	    md[i][d][(10*m+d)%7]=min(md[i][d][(10*m+d)%7], md[i-1][e][m]+p);
	  }
	}
      }
    }
  }
  int ans=1222333444;
  for (int d=0; d<=9; ++d){
    ans=min(ans, md[s.size()-1][d][0]);
  }
  cout << ans << "\n";
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED