public static void main ( String [ ] args ) {
  Scanner scn = new Scanner ( System . in ) ;
  long k = scn . nextLong ( ) , b = scn . nextLong ( ) , n = scn . nextLong ( ) , t = scn . nextLong ( ) ;
  long z = 1 , time = 0 ;
  ;
  while ( z <= t ) {
    z = z * k + b ;
    time ++ ;
  }
  long ans = n - time + 1 ;
  if ( ans < 0 ) {
    ans = 0 ;
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner scn = new Scanner ( System . in ) ; long k = scn . nextLong ( ) , b = scn . nextLong ( ) , n = scn . nextLong ( ) , t = scn . nextLong ( ) ; long z = 1 , time = 0 ; ; while ( z <= t ) { z = z * k + b ; time ++ ; } long ans = n - time + 1 ; if ( ans < 0 ) { ans = 0 ; } System . out . println ( ans ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal)) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (while_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) body: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (identifier)))) (expression_statement (update_expression (identifier))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (decimal_integer_literal)))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (decimal_integer_literal))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))