#include using namespace std; typedef signed long long ll; #undef _P #define _P(...) (void)printf(__VA_ARGS__) #define FOR(x,to) for(x=0;x<(to);x++) #define FORR(x,arr) for(auto& x:arr) #define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++) #define ALL(a) (a.begin()),(a.end()) #define ZERO(a) memset(a,0,sizeof(a)) #define MINUS(a) memset(a,0xff,sizeof(a)) //------------------------------------------------------- int H,W,K; string S[2020]; int C[2020][2020][26]; int PL[2020][2020]; int PR[2020][2020]; int num(int y,int x,int s) { int num=0,i; FOR(i,26) if(C[y+s][x+s][i]-C[y][x+s][i]-C[y+s][x][i]+C[y][x][i]>0) { num++; if(num>K) return num; if(num+(26-i)>H>>W>>K; FOR(y,H) { cin>>S[y]; FOR(x,W) { FOR(i,26) { C[y+1][x+1][i]=C[y][x+1][i]+C[y+1][x][i]-C[y][x][i]; if(S[y][x]=='a'+i) C[y+1][x+1][i]++; } } } ll ret=0; FOR(y,H) FOR(x,W) { int L=0,R=0; if(y&&x) { L=max(0,PL[y-1][x-1]-1); R=max(0,PR[y-1][x-1]-1); } while(y+L+1<=H&&x+L+1<=W&&num(y,x,L+1)