#pragma GCC target("avx")
//#pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define DB double
#define LD long double
#define ST string
#define BS bitset
#define PA pair<LL,LL>
#define VE vector
#define VL vector<LL>
#define VP vector<pair<LL,LL>>
#define VVL vector<vector<LL>>
#define PQ priority_queue
#define PQS priority_queue<LL,vector<LL>,greater<LL>>
#define PB push_back
#define POB pop_back
#define PF push_front
#define POF pop_front
#define EB emplace_back
#define MP make_pair
#define TS to_string
#define TU to_ullong
#define BPL __builtin_popcountll
#define FOR(i,a,n) for(i=a;i<n;++i)
#define FORR(i,a,n) for(i=n-1;i>=a;--i)
#define rep(i,n) FOR(i,0,n)
#define repr(i,n) FORR(i,0,n)
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define SORT(a) sort(ALL(a))
#define REV(a) reverse(ALL(a))
#define UB(a,n) *upper_bound(ALL(a),n)
#define UBn(a,n) upper_bound(ALL(a),n)-a.begin()
#define LB(a,n) *lower_bound(ALL(a),n)
#define LBn(a,n) lower_bound(ALL(a),n)-a.begin()
#define INF 1145141919810364364LL
#define PI 3.14159265358979
#define MOD 1000000007
//#define MOD 998244353
#define ERR 0.00000001
#define FAST cin.tie(0);ios::sync_with_stdio(false)

void Yn(LL a){if(a)printf("Yes\n");else printf("No\n");}
void YN(LL a){if(a)printf("YES\n");else printf("NO\n");}
LL pwmn(LL a,LL n){LL ans=1;while(ans<a)ans*=n;return ans;}
LL dig(LL n){LL ret=0;while(n)n/=10,ret++;return ret;}
LL GCD(LL a,LL b){LL c=1,tmp=max(a,b);b=min(a,b);a=tmp;while(c!=0){c=a%b;a=b;b=c;}return a;}
LL LCM(LL a,LL b){return a*b/GCD(a,b);}
int lcmp(const void* a,const void* b){if(*(LL*)a>*(LL*)b)return 1;if(*(LL*)a<*(LL*)b)return -1;return 0;}
int lcmpr(const void* a,const void* b){if(*(LL*)a>*(LL*)b)return -1;if(*(LL*)a<*(LL*)b)return 1;return 0;}
int ccmp(const void* a,const void* b){return *(char*)a-*(char*)b;}
int ccmpr(const void* a,const void* b){return *(char*)b-*(char*)a;}
int scmp(const void* a,const void* b){return strcmp((char*)a,(char*)b);}
int scmpr(const void* a,const void* b){return strcmp((char*)b,(char*)a);}
LL cmod(LL a,LL m){if(a%m<0)return a%m+abs(m);else return a%m;}
LL DIV(LL a,LL d,LL m){LL l=m,x=1,y=0,k;while(l){k=d/l;d-=k*l;swap(l,d);x-=k*y;swap(x,y);}return cmod(a*cmod(x,m),m);}
LL POW(LL a,LL n,LL m){LL ans=1;while(n>0){if(n&1)ans=ans*a%m;a=a*a%m;n>>=1;}return ans;}
VL fact,finv,inv;
void comi(LL n){LL i;fact.resize(max(2LL,n+1));finv.resize(max(2LL,n+1));inv.resize(max(2LL,n+1));fact[0]=fact[1]=1;finv[0]=finv[1]=1;inv[1]=1;FOR(i,2,n+1){fact[i]=fact[i-1]*i%MOD;inv[i]=MOD-inv[MOD%i]*(MOD/i)%MOD;finv[i]=finv[i-1]*inv[i]%MOD;}}
LL com(LL n,LL k){if(n<k||n<0||k<0)return 0;return fact[n]*(finv[k]*finv[n-k]%MOD)%MOD;}
bool cmps(pair<LL,LL> a,pair<LL,LL> b){if(a.second!=b.second)return a.second<b.second;return a.first<b.first;}
template<typename T>bool chmax(T &a,T b){if(a<b){a=b;return true;}return false;}
template<typename T>bool chmin(T &a,T b){if(a>b){a=b;return true;}return false;}

LL H,W,K,x_1,y_1,x_2,y_2;
VVL d;
queue<PA> q;
void BFS(){
	PA p=q.front();
	q.pop();
	LL i,x=p.first,y=p.second;
	//cout<<x<<" "<<y<<endl;
	FOR(i,1,K+1){
		if(x+i>=H||d[x+i][y]<=d[x][y])break;
		if(d[x+i][y]==d[x][y]+1)continue;
		d[x+i][y]=d[x][y]+1;
		q.push(MP(x+i,y));
		if(x+i==x_2&&y==y_2)while(!q.empty())q.pop();
	}
	FOR(i,1,K+1){
		if(x-i<0||d[x-i][y]<=d[x][y])break;
		if(d[x-i][y]==d[x][y]+1)continue;
		d[x-i][y]=d[x][y]+1;
		q.push(MP(x-i,y));
		if(x-i==x_2&&y==y_2)while(!q.empty())q.pop();
	}
	FOR(i,1,K+1){
		if(y+i>=W||d[x][y+i]<=d[x][y])break;
		if(d[x][y+i]==d[x][y]+1)continue;
		d[x][y+i]=d[x][y]+1;
		q.push(MP(x,y+i));
		if(x==x_2&&y+i==y_2)while(!q.empty())q.pop();
	}
	FOR(i,1,K+1){
		//cout<<x<<" "<<y-i<<endl;
		//cout<<d[x][y]<<endl;
		if(y-i<0||d[x][y-i]<=d[x][y])break;
		if(d[x][y-i]==d[x][y]+1)continue;
		d[x][y-i]=d[x][y]+1;
		q.push(MP(x,y-i));
		//cout<<"!"<<endl;
		if(x==x_2&&y-i==y_2)while(!q.empty())q.pop();
	}
}

int main(){
  FAST;
	LL i,j;
	cin>>H>>W>>K>>x_1>>y_1>>x_2>>y_2;
	ST c[H];
	rep(i,H)cin>>c[i];
	d.resize(H);
	rep(i,H)d[i].resize(W,INF);
	rep(i,H)rep(j,W)if(c[i][j]=='@')d[i][j]=-1;
	x_1--,y_1--,x_2--,y_2--;
	d[x_1][y_1]=0;
	q.push(MP(x_1,y_1));
	//cout<<"!"<<endl;
	while(!q.empty())BFS();
	if(d[x_2][y_2]==INF)d[x_2][y_2]=-1;
	cout<<d[x_2][y_2]<<endl;
}


Measured memory_bytes: 14148