Language: C

int main(){
	
	char a[8][9];
	int i,j,flag;

	while(scanf("%s",a[0])!=EOF){
		for(i=1;i<8;i++)
			scanf("%s",a[i]);
		
		flag=1;
		for(i=0;i<8&&flag;i++)
			for(j=0;j<8&&flag;j++)
				if(a[i][j]=='1'){
					if(i+1<8&&j+1<8&&a[i+1][j]=='1'&&a[i][j+1]=='1'&&a[i+1][j+1]=='1')
						printf("A\n");
					else if(i+3<8&&a[i+1][j]=='1'&&a[i+2][j]=='1'&&a[i+3][j]=='1')
						printf("B\n");
					else if(j+3<8&&a[i][j+1]=='1'&&a[i][j+2]=='1'&&a[i][j+3]=='1')
						printf("C\n");
					else if(i+2<8&&j-1>=0&&a[i+1][j-1]=='1'&&a[i+1][j]=='1'&&a[i+2][j-1]=='1')
						printf("D\n");
					else if(i+1<8&&j+2<8&&a[i][j+1]=='1'&&a[i+1][j+1]=='1'&&a[i+1][j+2]=='1')
						printf("E\n");
					else if(i+2<8&&j+1<8&&a[i+1][j]=='1'&&a[i+1][j+1]=='1'&&a[i+2][j+1]=='1')
						printf("F\n");
					else
						printf("G\n");
					flag=0;
				}
	}	
	return 0;
}

Compiler output:
main.c: In function 'main':
main.c:6:15: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    6 |         while(scanf("%s",a[0])!=EOF){
      |               ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | int main(){
main.c:6:15: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    6 |         while(scanf("%s",a[0])!=EOF){
      |               ^~~~~
main.c:6:15: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:6:33: error: 'EOF' undeclared (first use in this function)
    6 |         while(scanf("%s",a[0])!=EOF){
      |                                 ^~~
main.c:6:33: note: 'EOF' is defined in header '<stdio.h>'; this is probably fixable by adding '#include <stdio.h>'
main.c:6:33: note: each undeclared identifier is reported only once for each function it appears in
main.c:15:49: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   15 |                                                 printf("A\n");
      |                                                 ^~~~~~
main.c:15:49: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:15:49: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
main.c:15:49: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:17:49: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   17 |                                                 printf("B\n");
      |                                                 ^~~~~~
main.c:17:49: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:19:49: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   19 |                                                 printf("C\n");
      |                                                 ^~~~~~
main.c:19:49: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:21:49: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   21 |                                                 printf("D\n");
      |                                                 ^~~~~~
main.c:21:49: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:23:49: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   23 |                                                 printf("E\n");
      |                                                 ^~~~~~
main.c:23:49: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:25:49: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   25 |                                                 printf("F\n");
      |                                                 ^~~~~~
main.c:25:49: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:27:49: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
   27 |                                                 printf("G\n");
      |                                                 ^~~~~~
main.c:27:49: note: include '<stdio.h>' or provide a declaration of 'printf'